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+</style><link href="http://www.w3.org/StyleSheets/TR/w3c-unofficial" rel="stylesheet" type="text/css" charset="utf-8" /></head>
+
+<body style="display: inherit; "><div class="head"><p></p><h1 class="title" id="title">The JSON-LD API 1.0</h1><h2 id="subtitle">An Application Programming Interface for the JSON-LD Syntax</h2><h2 id="unofficial-draft-24-october-2011">Unofficial Draft 24 October 2011</h2><dl><dt>Editors:</dt><dd><a href="http://manu.sporny.org/">Manu Sporny</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, <a href="http://kellogg-assoc.com/">Kellogg Associates</a></dd>
+<dd><a href="http://digitalbazaar.com/">Dave Longley</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dt>Authors:</dt><dd><a href="http://digitalbazaar.com/">Dave Longley</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dd><a href="http://digitalbazaar.com/">Manu Sporny</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, <a href="http://kellogg-assoc.com/">Kellogg Associates</a></dd>
+</dl><p>This document is also available in this non-normative format: <a href="diff-20111016.html">diff to previous version</a>.</p><p class="copyright">This document is licensed under a <a class="subfoot" href="http://creativecommons.org/licenses/by/3.0/" rel="license">Creative Commons Attribution 3.0 License</a>.</p><hr /></div>
+<div id="abstract" class="introductory section"><h2>Abstract</h2>
+<p>
+JSON [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>] has proven to be a highly useful object serialization and
+messaging format. JSON-LD [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-LD">JSON-LD</a></cite>] harmonizes the representation of
+Linked Data in JSON by outlining a common JSON representation format for
+expressing directed graphs; mixing both Linked Data and non-Linked Data in
+a single document. This document outlines an Application Programming
+Interface and a set of algorithms for programmatically transforming
+JSON-LD documents.
+</p>
+</div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p>This document is merely a public working draft of a potential specification. It has no official standing of any kind and does not represent the support or consensus of any standards organisation.</p>
+<p>This document is an experimental work in progress.</p>
+
+<!-- <p>
+This document has been reviewed by W3C Members, by software
+developers, and by other W3C groups and interested parties, and is
+endorsed by the Director as a W3C Recommendation. It is a stable
+document and may be used as reference material or cited from another
+document. W3C's role in making the Recommendation is to draw attention
+to the specification and to promote its widespread deployment. This
+enhances the functionality and interoperability of the Web.
+</p> -->
+
+</div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a><ul class="toc"><li class="tocline"><a href="#how-to-read-this-document" class="tocxref"><span class="secno">1.1 </span>How to Read this Document</a></li><li class="tocline"><a href="#linked-data" class="tocxref"><span class="secno">1.2 </span>Linked Data</a></li><li class="tocline"><a href="#contributing" class="tocxref"><span class="secno">1.3 </span>Contributing</a></li></ul></li><li class="tocline"><a href="#the-application-programming-interface" class="tocxref"><span class="secno">2. </span>The Application Programming Interface</a><ul class="toc"><li class="tocline"><a href="#jsonldprocessor" class="tocxref"><span class="secno">2.1 </span>JsonLdProcessor</a><ul class="toc"><li class="tocline"><a href="#methods" class="tocxref"><span class="secno">2.1.1 </span>Methods</a></li></ul></li><li class="tocline"><a href="#jsonldtriplecallback" class="tocxref"><span class="secno">2.2 </span>JsonLdTripleCallback</a><ul class="toc"><li class="tocline"><a href="#methods-1" class="tocxref"><span class="secno">2.2.1 </span>Methods</a></li></ul></li></ul></li><li class="tocline"><a href="#algorithms" class="tocxref"><span class="secno">3. </span>Algorithms</a><ul class="toc"><li class="tocline"><a href="#syntax-tokens-and-keywords" class="tocxref"><span class="secno">3.1 </span>Syntax Tokens and Keywords</a></li><li class="tocline"><a href="#algorithm-terms" class="tocxref"><span class="secno">3.2 </span>Algorithm Terms</a></li><li class="tocline"><a href="#context-1" class="tocxref"><span class="secno">3.3 </span>Context</a></li><li class="tocline"><a href="#value-compaction" class="tocxref"><span class="secno">3.4 </span>Value Compaction</a></li><li class="tocline"><a href="#expansion" class="tocxref"><span class="secno">3.5 </span>Expansion</a><ul class="toc"><li class="tocline"><a href="#expansion-algorithm" class="tocxref"><span class="secno">3.5.1 </span>Expansion Algorithm</a></li></ul></li><li class="tocline"><a href="#compaction" class="tocxref"><span class="secno">3.6 </span>Compaction</a><ul class="toc"><li class="tocline"><a href="#compaction-algorithm" class="tocxref"><span class="secno">3.6.1 </span>Compaction Algorithm</a></li></ul></li><li class="tocline"><a href="#framing" class="tocxref"><span class="secno">3.7 </span>Framing</a><ul class="toc"><li class="tocline"><a href="#framing-algorithm-terms" class="tocxref"><span class="secno">3.7.1 </span>Framing Algorithm Terms</a></li><li class="tocline"><a href="#framing-algorithm" class="tocxref"><span class="secno">3.7.2 </span>Framing Algorithm</a></li></ul></li><li class="tocline"><a href="#normalization" class="tocxref"><span class="secno">3.8 </span>Normalization</a><ul class="toc"><li class="tocline"><a href="#normalization-algorithm-terms" class="tocxref"><span class="secno">3.8.1 </span>Normalization Algorithm Terms</a></li><li class="tocline"><a href="#normalization-state" class="tocxref"><span class="secno">3.8.2 </span>Normalization State</a></li><li class="tocline"><a href="#normalization-algorithm" class="tocxref"><span class="secno">3.8.3 </span>Normalization Algorithm</a></li><li class="tocline"><a href="#node-relabeling-algorithm" class="tocxref"><span class="secno">3.8.4 </span>Node Relabeling Algorithm</a></li><li class="tocline"><a href="#deterministic-labeling-algorithm" class="tocxref"><span class="secno">3.8.5 </span>Deterministic Labeling Algorithm</a></li><li class="tocline"><a href="#shallow-comparison-algorithm" class="tocxref"><span class="secno">3.8.6 </span>Shallow Comparison Algorithm</a></li><li class="tocline"><a href="#object-comparison-algorithm" class="tocxref"><span class="secno">3.8.7 </span>Object Comparison Algorithm</a></li><li class="tocline"><a href="#deep-comparison-algorithm" class="tocxref"><span class="secno">3.8.8 </span>Deep Comparison Algorithm</a></li><li class="tocline"><a href="#node-serialization-algorithm" class="tocxref"><span class="secno">3.8.9 </span>Node Serialization Algorithm</a></li><li class="tocline"><a href="#serialization-label-generation-algorithm" class="tocxref"><span class="secno">3.8.10 </span>Serialization Label Generation Algorithm</a></li><li class="tocline"><a href="#combinatorial-serialization-algorithm" class="tocxref"><span class="secno">3.8.11 </span>Combinatorial Serialization Algorithm</a></li><li class="tocline"><a href="#serialization-comparison-algorithm" class="tocxref"><span class="secno">3.8.12 </span>Serialization Comparison Algorithm</a></li><li class="tocline"><a href="#mapping-serialization-algorithm" class="tocxref"><span class="secno">3.8.13 </span>Mapping Serialization Algorithm</a></li><li class="tocline"><a href="#label-serialization-algorithm" class="tocxref"><span class="secno">3.8.14 </span>Label Serialization Algorithm</a></li></ul></li><li class="tocline"><a href="#data-round-tripping" class="tocxref"><span class="secno">3.9 </span>Data Round Tripping</a></li><li class="tocline"><a href="#rdf-conversion" class="tocxref"><span class="secno">3.10 </span>RDF Conversion</a><ul class="toc"><li class="tocline"><a href="#overview" class="tocxref"><span class="secno">3.10.1 </span>Overview</a></li><li class="tocline"><a href="#rdf-conversion-algorithm-terms" class="tocxref"><span class="secno">3.10.2 </span>RDF Conversion Algorithm Terms</a></li><li class="tocline"><a href="#rdf-conversion-algorithm" class="tocxref"><span class="secno">3.10.3 </span>RDF Conversion Algorithm</a></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">3.10.4 </span>Acknowledgements</a></li></ul></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">A. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">A.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">A.2 </span>Informative references</a></li></ul></li></ul></div>
+
+
+
+<div id="introduction" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">1. </span>Introduction</h2>
+
+<p>
+JSON, as specified in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>], is a simple language for representing
+data on the Web. Linked Data is a technique for creating a graph of interlinked data across
+different
+documents or Web sites. Data entities are described using <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s,
+which are typically dereferencable and thus may be used to find more
+information about an entity, creating a "Web of Knowledge". JSON-LD is intended to be a simple
+publishing method for expressing not only Linked Data in JSON, but also for adding
+semantics to existing JSON.
+</p>
+
+<p>
+JSON-LD is designed as a light-weight syntax that can be used to express
+Linked Data. It is primarily intended to be a way to use Linked Data
+in Javascript and other Web-based programming environments. It is also
+useful when building interoperable Web services and when storing Linked
+Data in JSON-based document storage engines. It is practical and designed
+to be as simple as possible, utilizing the large number of JSON parsers
+and libraries available today. It is designed to be able to
+express key-value pairs, RDF data, RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] data, Microformats
+[<cite><a class="bibref" rel="biblioentry" href="#bib-MICROFORMATS">MICROFORMATS</a></cite>] data, and Microdata [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]. That is, it supports
+every major Web-based structured data model in use today.
+</p>
+
+<p>
+The syntax does not necessarily require applications to change their JSON, but
+allows to easily add meaning by adding context in a way that is either in-band or
+out-of-band. The syntax is designed to not disturb already deployed systems
+running on JSON, but provide a smooth upgrade path from JSON to JSON with
+added semantics. Finally, the format is intended to be easy to parse, efficient to
+generate, convertible to RDF in one pass, and require a very small memory footprint
+in order to operate.
+</p>
+
+<div id="how-to-read-this-document" class="section">
+<h3><span class="secno">1.1 </span>How to Read this Document</h3>
+
+<p>
+This document is a detailed specification for a serialization of Linked
+Data in JSON. The document is primarily intended for the following audiences:
+</p>
+
+<ul>
+ <li>Authors that want a very detailed view of how JSON-LD processors
+ operate.</li>
+ <li>Software developers that want to implement processors and APIs for
+ JSON-LD.</li>
+</ul>
+
+<p>
+To understand the basics in this specification you must first be familiar with
+JSON, which is detailed in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>]. You must also understand the
+JSON-LD Syntax [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-LD">JSON-LD</a></cite>], which is the base syntax used by all of the
+algorithms in this document. To understand the API and how it is
+intended to operate in a programming environment, it is useful to have working
+knowledge of the JavaScript programming language [<cite><a class="bibref" rel="biblioentry" href="#bib-ECMA-262">ECMA-262</a></cite>] and
+WebIDL [<cite><a class="bibref" rel="biblioentry" href="#bib-WEBIDL">WEBIDL</a></cite>]. To understand how JSON-LD maps to RDF, it is helpful to be
+familiar with the basic RDF concepts [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>].</p>
+
+<p>
+ Examples may contain references to existing vocabularies and use <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es to refer to Web Vocabularies. The following is a list of all vocabularies and their <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> abbreviations, as used in this document:
+</p>
+<ul>
+ <li>The <a href="http://purl.org/dc/terms/">Dublin Core</a>
+ vocabulary (abbreviation: <code>dc</code>, e.g., <code>dc:title</code>)</li>
+ <li>The <a href="http://xmlns.com/foaf/0.1/">Friend of a Friend</a>
+ vocabulary (abbreviation: <code>foaf</code>, e.g., <code>foaf:knows</code>)</li>
+ <li>The <a href="http://www.w3.org/1999/02/22-rdf-syntax-ns#">RDF</a>
+ vocabulary (abbreviation: <code>rdf</code>, e.g., <code>rdf:type</code>)</li>
+ <li>The <a href="http://www.w3.org/2001/XMLSchema#">XSD</a>
+ vocabulary (abbreviation: <code>xsd</code>, e.g., <code>xsd:integer</code>)</li>
+</ul>
+
+<p>
+ JSON [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>] defines several terms which are used throughout this document:
+ </p><dl>
+ <dt><dfn title="json_object" id="dfn-json_object">JSON Object</dfn></dt><dd>
+ An object structure is represented as a pair of curly brackets surrounding zero or
+ more name/value pairs (or members). A name is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>. A single colon comes after
+ each name, separating the name from the value. A single comma separates a value
+ from a following name. The names within an object <em class="rfc2119" title="should">should</em> be unique.
+ </dd>
+ <dt><dfn title="array" id="dfn-array">array</dfn></dt>
+ <dd>
+ An array is an ordered collection of values. An array structure is represented as square brackets surrounding zero or more values (or elements). Elements are separated by commas. Within JSON-LD, array order is not preserved by default, unless
+ specific markup is provided (see <a href="#lists">Lists</a>). This is because the basic data model of JSON-LD
+ is a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a>, which is inherently unordered.
+ </dd>
+ <dt><dfn title="string" id="dfn-string">string</dfn></dt><dd>
+ A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A
+ character is represented as a single character string.
+ </dd>
+ <dt><dfn title="number" id="dfn-number">number</dfn></dt>
+ <dd>
+ A number is is similar to that used in most programming languages, except that the octal and hexadecimal formats are not used and that leading zeros are not allowed.</dd>
+ <dt><dfn title="true" id="dfn-true">true</dfn> and <dfn title="false" id="dfn-false">false</dfn></dt><dd>
+ Boolean values.
+ </dd>
+ <dt><dfn title="null" id="dfn-null">null</dfn></dt><dd>
+ The use of the <em>null</em> value is undefined within JSON-LD.
+ <div class="issue">Supporting <em>null</em> in JSON-LD might have a number of advantages and should be evaluated. This is currently an <a href="https://github.com/json-ld/json-ld.org/issues/11">open issue</a>.</div>
+ </dd>
+ </dl>
+<p></p>
+</div>
+
+<div id="linked-data" class="section">
+<h3><span class="secno">1.2 </span>Linked Data</h3>
+<p>
+The following definition for <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> is the one that will
+be used for this specification.
+</p>
+<ol>
+ <li><dfn title="linked_data" id="dfn-linked_data">Linked Data</dfn> is a set of documents, each containing a representation of a linked data graph.</li>
+ <li>A <dfn title="linked_data_graph" id="dfn-linked_data_graph">linked data graph</dfn> is an unordered labeled directed graph, where nodes are <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>s or <a class="tref internalDFN" title="object" href="#dfn-object">object</a>s, and edges are properties.</li>
+ <li>A <dfn title="subject" id="dfn-subject">subject</dfn> is any node in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> with at least one outgoing edge.</li>
+ <li>A <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> <em class="rfc2119" title="should">should</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> (an Internationalized Resource Identifier as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>]).</li>
+ <li>An <dfn title="object" id="dfn-object">object</dfn> is a node in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> with at least one incoming edge.</li>
+ <li>An <a class="tref internalDFN" title="object" href="#dfn-object">object</a> <em class="rfc2119" title="may">may</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</li>
+ <li>An object <em class="rfc2119" title="may">may</em> be a <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> and <a class="tref internalDFN" title="object" href="#dfn-object">object</a> at the same time.</li>
+ <li>A <dfn title="property" id="dfn-property">property</dfn> is an edge of the <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a>.</li>
+ <li>A <a class="tref internalDFN" title="property" href="#dfn-property">property</a> <em class="rfc2119" title="should">should</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> that is a label in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> <em class="rfc2119" title="should">should</em> be dereferencable to a <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> document describing the labeled <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>, <a class="tref internalDFN" title="object" href="#dfn-object">object</a> or <a class="tref internalDFN" title="property" href="#dfn-property">property</a>.</li>
+ <li>A <dfn title="literal" id="dfn-literal">literal</dfn> is an <a class="tref internalDFN" title="object" href="#dfn-object">object</a> with a label that is not an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a></li>
+</ol>
+
+<p>
+Note that the definition for <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> above is silent on the
+topic of unlabeled nodes. Unlabeled nodes are not considered
+<a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>. However, this specification allows for the expression
+of unlabled nodes, as most graph-based data sets on the Web contain a number
+of associated nodes that are not named and thus are not directly
+de-referenceable.
+</p>
+</div>
+
+<div id="contributing" class="section">
+<h3><span class="secno">1.3 </span>Contributing</h3>
+
+<p>There are a number of ways that one may participate in the development of
+this specification:</p>
+
+<ul>
+<li>Technical discussion typically occurs on the public mailing list:
+<a href="http://lists.w3.org/Archives/Public/public-linked-json/">public-linked-json@w3.org</a>
+</li>
+
+<li><a href="http://json-ld.org/minutes/">Public teleconferences</a> are held
+on Tuesdays at 1500UTC on the second and fourth week of each month.
+</li>
+
+<li>Specification bugs and issues should be reported in the
+<a href="https://github.com/json-ld/json-ld.org/issues">issue tracker</a>.</li>
+
+<li><a href="https://github.com/json-ld/json-ld.org/tree/master/spec">Source code</a> for the
+specification can be found on Github.</li>
+
+<li>The <a href="http://webchat.freenode.net/?channels=#json-ld">#json-ld</a>
+IRC channel is available for real-time discussion on irc.freenode.net.</li>
+</ul>
+
+</div>
+
+</div>
+
+<div id="the-application-programming-interface" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">2. </span>The Application Programming Interface</h2>
+
+<p>This API provides a clean mechanism that enables developers to convert
+JSON-LD data into a a variety of output formats that are easier to work with in
+various programming languages. If a JSON-LD API is provided in a programming
+environment, the entirety of the following API <em class="rfc2119" title="must">must</em> be implemented.
+</p>
+
+<div id="jsonldprocessor" class="section">
+<h3><span class="secno">2.1 </span>JsonLdProcessor</h3>
+<pre class="idl"><span class="idlInterface" id="idl-def-JsonLdProcessor">[<span class="extAttr">NoInterfaceObject</span>]
+interface <span class="idlInterfaceID">JsonLdProcessor</span> {
+<span class="idlMethod"> <span class="idlMethType"><a>object</a></span> <span class="idlMethName"><a href="#widl-JsonLdProcessor-expand-object-object-input-object-context">expand</a></span> (<span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">input</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>object</a>?</span> <span class="idlParamName">context</span></span>) raises (<span class="idlRaises"><a>InvalidContext</a></span>);</span>
+<span class="idlMethod"> <span class="idlMethType"><a>object</a></span> <span class="idlMethName"><a href="#widl-JsonLdProcessor-compact-object-object-input-object-context">compact</a></span> (<span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">input</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>object</a>?</span> <span class="idlParamName">context</span></span>) raises (<span class="idlRaises"><a>InvalidContext</a></span>, <span class="idlRaises"><a>ProcessingError</a></span>);</span>
+<span class="idlMethod"> <span class="idlMethType"><a>object</a></span> <span class="idlMethName"><a href="#widl-JsonLdProcessor-frame-object-object-input-object-frame-object-options">frame</a></span> (<span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">input</span></span>, <span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">frame</span></span>, <span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">options</span></span>) raises (<span class="idlRaises"><a>InvalidFrame</a></span>);</span>
+<span class="idlMethod"> <span class="idlMethType"><a>object</a></span> <span class="idlMethName"><a href="#widl-JsonLdProcessor-normalize-object-object-input-object-context">normalize</a></span> (<span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">input</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>object</a>?</span> <span class="idlParamName">context</span></span>) raises (<span class="idlRaises"><a>InvalidContext</a></span>);</span>
+<span class="idlMethod"> <span class="idlMethType"><a>object</a></span> <span class="idlMethName"><a href="#widl-JsonLdProcessor-triples-object-object-input-JsonLdTripleCallback-tripleCallback-object-context">triples</a></span> (<span class="idlParam"><span class="idlParamType"><a>object</a></span> <span class="idlParamName">input</span></span>, <span class="idlParam"><span class="idlParamType"><a href="#idl-def-JsonLdTripleCallback" class="idlType"><code>JsonLdTripleCallback</code></a></span> <span class="idlParamName">tripleCallback</span></span>, <span class="idlParam">optional <span class="idlParamType"><a>object</a>?</span> <span class="idlParamName">context</span></span>) raises (<span class="idlRaises"><a>InvalidContext</a></span>);</span>
+};</span>
+</pre><div id="methods" class="section"><h4><span class="secno">2.1.1 </span>Methods</h4><dl class="methods"><dt id="widl-JsonLdProcessor-compact-object-object-input-object-context"><code>compact</code></dt><dd><a href="#compaction">Compacts</a> the given <code>input</code>
+ according to the steps in the
+ <a href="#compaction-algorithm">Compaction Algorithm</a>. The
+ <code>input</code> <em class="rfc2119" title="must">must</em> be copied, compacted and returned if there are
+ no errors. If the compaction fails, an appropirate exception <em class="rfc2119" title="must">must</em> be
+ thrown.
+
+
+
+
+
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">input</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The JSON-LD object to perform compaction on.</td></tr><tr><td class="prmName">context</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptTrue">✔</td><td class="prmDesc">The base context to use when compacting the <code>input</code>.</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a>InvalidContext</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>INVALID_SYNTAX</code></td><td class="excCodeDesc">A general syntax error was detected in the <code>@context</code>.
+ For example, if a <code>@coerce</code> key maps to anything other than
+ a string or an array of strings, this exception would be raised.</td></tr><tr><td class="excCodeName"><code>MULTIPLE_DATATYPES</code></td><td class="excCodeDesc">There is more than one target datatype specified for a single
+ property in the list of coercion rules. This means that the processor
+ does not know what the developer intended for the target datatype for a
+ property.</td></tr></table></td></tr><tr><td class="excName"><a>ProcessingError</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>LOSSY_COMPACTION</code></td><td class="excCodeDesc">The compaction would lead to a loss of information, such as a
+ <code>@language</code> value.</td></tr><tr><td class="excCodeName"><code>CONFLICTING_DATATYPES</code></td><td class="excCodeDesc">The target datatype specified in the coercion rule and the
+ datatype for the typed literal do not match.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>object</a></code></div></dd><dt id="widl-JsonLdProcessor-expand-object-object-input-object-context"><code>expand</code></dt><dd><a href="#expansion">Expands</a> the given <code>input</code>
+ according to the steps in the
+ <a href="#expansion-algorithm">Expansion Algorithm</a>. The
+ <code>input</code> <em class="rfc2119" title="must">must</em> be copied, expanded and returned if there are
+ no errors. If the expansion fails, an appropriate exception <em class="rfc2119" title="must">must</em> be thrown.
+
+
+
+
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">input</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The JSON-LD object to copy and perform the expansion upon.</td></tr><tr><td class="prmName">context</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptTrue">✔</td><td class="prmDesc">An external context to use additionally to the context embedded in <code>input</code> when expanding the <code>input</code>.</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a>InvalidContext</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>INVALID_SYNTAX</code></td><td class="excCodeDesc">A general syntax error was detected in the <code>@context</code>.
+ For example, if a <code>@coerce</code> key maps to anything other than
+ a string or an array of strings, this exception would be raised.</td></tr><tr><td class="excCodeName"><code>MULTIPLE_DATATYPES</code></td><td class="excCodeDesc">There is more than one target datatype specified for a single
+ property in the list of coercion rules. This means that the processor
+ does not know what the developer intended for the target datatype for a
+ property.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>object</a></code></div></dd><dt id="widl-JsonLdProcessor-frame-object-object-input-object-frame-object-options"><code>frame</code></dt><dd><a href="#framing">Frames</a> the given <code>input</code>
+ using the <code>frame</code> according to the steps in the
+ <a href="#framing-algorithm">Framing Algorithm</a>. The
+ <code>input</code> is used to build the framed output and is returned if
+ there are no errors. If there are no matches for the frame,
+ <code>null</code> <em class="rfc2119" title="must">must</em> be returned. Exceptions <em class="rfc2119" title="must">must</em> be thrown if there are
+ errors.
+
+
+
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">input</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The JSON-LD object to perform framing on.</td></tr><tr><td class="prmName">frame</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The frame to use when re-arranging the data.</td></tr><tr><td class="prmName">options</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">A set of options that will affect the framing algorithm.</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a>InvalidFrame</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>INVALID_SYNTAX</code></td><td class="excCodeDesc">A frame must be either an object or an array of objects, if the frame
+ is neither of these types, this exception is thrown.</td></tr><tr><td class="excCodeName"><code>MULTIPLE_EMBEDS</code></td><td class="excCodeDesc">A subject IRI was specified in more than one place in the input
+ frame. More than one embed of a given subject IRI is not allowed, and if
+ requested, <em class="rfc2119" title="must">must</em> result in this exception.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>object</a></code></div></dd><dt id="widl-JsonLdProcessor-normalize-object-object-input-object-context"><code>normalize</code></dt><dd><a href="#normalization">Normalizes</a> the given <code>input</code>
+ according to the steps in the
+ <a href="#normalization-algorithm">Normalization Algorithm</a>. The
+ <code>input</code> <em class="rfc2119" title="must">must</em> be copied, normalized and returned if there are
+ no errors. If the compaction fails, <code>null</code> <em class="rfc2119" title="must">must</em> be returned.
+
+
+
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">input</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The JSON-LD object to perform normalization upon.</td></tr><tr><td class="prmName">context</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptTrue">✔</td><td class="prmDesc">An external context to use additionally to the context embedded in <code>input</code> when expanding the <code>input</code>.</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a>InvalidContext</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>INVALID_SYNTAX</code></td><td class="excCodeDesc">A general syntax error was detected in the <code>@context</code>.
+ For example, if a <code>@coerce</code> key maps to anything other than
+ a string or an array of strings, this exception would be raised.</td></tr><tr><td class="excCodeName"><code>MULTIPLE_DATATYPES</code></td><td class="excCodeDesc">There is more than one target datatype specified for a single
+ property in the list of coercion rules. This means that the processor
+ does not know what the developer intended for the target datatype for a
+ property.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>object</a></code></div></dd><dt id="widl-JsonLdProcessor-triples-object-object-input-JsonLdTripleCallback-tripleCallback-object-context"><code>triples</code></dt><dd>Processes the <code>input</code> according to the
+ <a href="#rdf-conversion-algorithm">RDF Conversion Algorithm</a>, calling
+ the provided <code>tripleCallback</code> for each triple generated.
+
+
+
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">input</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The JSON-LD object to process when outputting triples.</td></tr><tr><td class="prmName">tripleCallback</td><td class="prmType"><code><a href="#idl-def-JsonLdTripleCallback" class="idlType"><code>JsonLdTripleCallback</code></a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">A callback that is called whenever a processing error occurs on
+ the given <code>input</code>.
+ <div class="issue">This callback should be aligned with the
+ RDF API.</div></td></tr><tr><td class="prmName">context</td><td class="prmType"><code><a>object</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptTrue">✔</td><td class="prmDesc">An external context to use additionally to the context embedded in <code>input</code> when expanding the <code>input</code>.</td></tr></table><table class="exceptions"><tr><th>Exception</th><th>Description</th></tr><tr><td class="excName"><a>InvalidContext</a></td><td class="excDesc"><table class="exceptionCodes"><tr><td class="excCodeName"><code>INVALID_SYNTAX</code></td><td class="excCodeDesc">A general syntax error was detected in the <code>@context</code>.
+ For example, if a <code>@coerce</code> key maps to anything other than
+ a string or an array of strings, this exception would be raised.</td></tr><tr><td class="excCodeName"><code>MULTIPLE_DATATYPES</code></td><td class="excCodeDesc">There is more than one target datatype specified for a single
+ property in the list of coercion rules. This means that the processor
+ does not know what the developer intended for the target datatype for a
+ property.</td></tr></table></td></tr></table><div><em>Return type: </em><code><a>object</a></code></div></dd></dl></div>
+
+</div>
+
+<div id="jsonldtriplecallback" class="section">
+<h3><span class="secno">2.2 </span>JsonLdTripleCallback</h3>
+<p>The JsonLdTripleCallback is called whenever the processor generates a
+triple during the <code>triple()</code> call.</p>
+
+<pre class="idl"><span class="idlInterface" id="idl-def-JsonLdTripleCallback">[<span class="extAttr">NoInterfaceObject Callback</span>]
+interface <span class="idlInterfaceID">JsonLdTripleCallback</span> {
+<span class="idlMethod"> <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-JsonLdTripleCallback-triple-void-DOMString-subject-DOMString-property-DOMString-objectType-DOMString-object-DOMString-datatype-DOMString-language">triple</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">subject</span></span>, <span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">property</span></span>, <span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">objectType</span></span>, <span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">object</span></span>, <span class="idlParam"><span class="idlParamType"><a>DOMString</a>?</span> <span class="idlParamName">datatype</span></span>, <span class="idlParam"><span class="idlParamType"><a>DOMString</a>?</span> <span class="idlParamName">language</span></span>);</span>
+};</span>
+</pre><div id="methods-1" class="section"><h4><span class="secno">2.2.1 </span>Methods</h4><dl class="methods"><dt id="widl-JsonLdTripleCallback-triple-void-DOMString-subject-DOMString-property-DOMString-objectType-DOMString-object-DOMString-datatype-DOMString-language"><code>triple</code></dt><dd>This callback is invoked whenever a triple is generated by the processor.
+
+ <table class="parameters"><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">subject</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The subject IRI that is associated with the triple.</td></tr><tr><td class="prmName">property</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The property IRI that is associated with the triple.</td></tr><tr><td class="prmName">objectType</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The type of object that is associated with the triple. Valid values
+ are <code>IRI</code> and <code>literal</code>.</td></tr><tr><td class="prmName">object</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullFalse">✘</td><td class="prmOptFalse">✘</td><td class="prmDesc">The object value associated with the subject and the property.</td></tr><tr><td class="prmName">datatype</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptFalse">✘</td><td class="prmDesc">The datatype associated with the object.</td></tr><tr><td class="prmName">language</td><td class="prmType"><code><a>DOMString</a></code></td><td class="prmNullTrue">✔</td><td class="prmOptFalse">✘</td><td class="prmDesc">The language associated with the object in BCP47 format.</td></tr></table><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>void</a></code></div></dd></dl></div>
+</div>
+
+
+</div>
+
+<div id="algorithms" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">3. </span>Algorithms</h2>
+
+<p>All algorithms described in this section are intended to operate on
+language-native data structures. That is, the serialization to a text-based
+JSON document isn't required as input or output to any of these algorithms and
+language-native data structures <em class="rfc2119" title="must">must</em> be used where applicable.</p>
+
+<div id="syntax-tokens-and-keywords" class="section">
+ <h3><span class="secno">3.1 </span>Syntax Tokens and Keywords</h3>
+
+ <p>JSON-LD specifies a number of syntax tokens and keywords that are using
+ in all algorithms described in this section:</p>
+
+ <dl>
+ <dt><code>@context</code></dt><dd>Used to set the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.</dd>
+ <dt><code>@base</code></dt><dd>Used to set the base IRI for all object IRIs affected by the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</dd>
+ <dt><code>@vocab</code></dt><dd>Used to set the base IRI for all property IRIs affected by the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</dd>
+ <dt><code>@coerce</code></dt><dd>Used to specify type coercion rules.</dd>
+ <dt><code>@literal</code></dt><dd>Used to specify a literal value.</dd>
+ <dt><code>@iri</code></dt><dd>Used to specify an IRI value.</dd>
+ <dt><code>@language</code></dt><dd>Used to specify the language for a literal.</dd>
+ <dt><code>@datatype</code></dt><dd>Used to specify the datatype for a literal.</dd>
+ <dt><code>:</code></dt><dd>The separator for JSON keys and values that use the <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> mechanism.</dd>
+ <dt><code>@subject</code></dt><dd>Sets the active subject.</dd>
+ <dt><code>@type</code></dt><dd>Used to set the type of the active subject.</dd>
+ </dl>
+</div>
+
+<div id="algorithm-terms" class="section">
+ <h3><span class="secno">3.2 </span>Algorithm Terms</h3>
+ <dl>
+ <dt><dfn title="initial_context" id="dfn-initial_context">initial context</dfn></dt>
+ <dd>
+ a context that is specified to the algorithm before processing begins.
+ </dd>
+ <dt><dfn title="active_subject" id="dfn-active_subject">active subject</dfn></dt>
+ <dd>
+ the currently active subject that the processor should use when
+ processing.
+ </dd>
+ <dt><dfn title="active_property" id="dfn-active_property">active property</dfn></dt>
+ <dd>
+ the currently active property that the processor should use when
+ processing.
+ </dd>
+ <dt><dfn title="active_object" id="dfn-active_object">active object</dfn></dt>
+ <dd>
+ the currently active object that the processor should use when
+ processing.
+ </dd>
+ <dt><dfn title="active_context" id="dfn-active_context">active context</dfn></dt>
+ <dd>
+ a context that is used to resolve <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s while the processing
+ algorithm is running. The <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> is the context
+ contained within the <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>.
+ </dd>
+ <dt><dfn title="local_context" id="dfn-local_context">local context</dfn></dt>
+ <dd>
+ a context that is specified within a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>,
+ specified via the <code>@context</code> keyword.
+ </dd>
+ <dt><dfn title="processor_state" id="dfn-processor_state">processor state</dfn></dt>
+ <dd>
+ the <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>, which includes the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active
+ context</a>, <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, and
+ <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>. The <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> is managed
+ as a stack with elements from the previous <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>
+ copied into a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> when entering a new
+ <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>.
+ </dd>
+ <dt><dfn title="json-ld_input" id="dfn-json-ld_input">JSON-LD input</dfn></dt>
+ <dd>
+ The JSON-LD data structure that is provided as input to the algorithm.
+ </dd>
+ <dt><dfn title="json-ld_output" id="dfn-json-ld_output">JSON-LD output</dfn></dt>
+ <dd>
+ The JSON-LD data structure that is produced as output by the algorithm.
+ </dd>
+ <dt><dfn title="term" id="dfn-term">term</dfn></dt><dd>
+ A <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is a short word defined with a <a href="#context">context</a> that <em class="rfc2119" title="may">may</em> be expanded
+ to an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>
+ </dd>
+ <dt><dfn title="prefix" id="dfn-prefix">prefix</dfn></dt><dd>
+ A <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> is a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> that expands to a Web Vocabulary base IRI. It
+ is typically used along with a <em>suffix</em> to create an IRI within a Web Vocabulary.
+ </dd>
+ <dt><dfn title="plain_literal" id="dfn-plain_literal">plain literal</dfn></dt><dd>
+ A <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a> is a <a class="tref internalDFN" title="literal" href="#dfn-literal">literal</a> without a datatype, possibly including
+ a language.
+ </dd>
+ <dt><dfn title="typed_literal" id="dfn-typed_literal">typed literal</dfn></dt><dd>
+ A <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> is a <a class="tref internalDFN" title="literal" href="#dfn-literal">literal</a> with an associated <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>
+ which indicates the literal's datatype.
+ </dd>
+ </dl>
+</div>
+
+<div id="context-1" class="section">
+ <h3 id="context"><span class="secno">3.3 </span>Context</h3>
+ <p>
+ Processing of JSON-LD data structure is managed recursively.
+ During processing, each rule is applied using information provided by the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.
+ Processing begins by pushing a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> onto the <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> stack and
+ initializing the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> with the <a class="tref internalDFN" title="initial_context" href="#dfn-initial_context">initial context</a>. If a <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> is encountered,
+ information from the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> is merged into the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.
+ </p>
+ <p>
+ The <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> is used for expanding keys and values of a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> (or elements
+ of a list (see <span a="#list-processing">List Processing</span>)).
+ </p>
+ <p>
+ A <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> is identified within a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> having a key of
+ <code>@context</code> with <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, <a class="tref internalDFN" title="array" href="#dfn-array">array</a> or a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> value. When processing a <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>, special processing rules apply:
+ </p>
+ <ol class="algorithm">
+ <li>Create a new, empty <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.</li>
+ <li>Let <em>value</em> be the value of <code>@context</code></li>
+ <ol id="process-context" class="algorithm">
+ <li>If <em>value</em> is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, process
+ each element as <em>value</em>, in order using <a href="#process-context">Step 2</a>.
+ </li><li>
+ If <em>value</em> is a simple <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, it <em class="rfc2119" title="must">must</em> have a lexical form of IRI.
+ <ol class="algorithm">
+ <li>Set <em>value</em> to the result of performing <a href="#iri-expansion">IRI Expansion</a>
+ on <em>value</em>.
+ </li><li>If <em>value</em> does is not an absolute IRI, abort this processing step.
+ Otherwise, Dereference <em>value</em>.</li>
+ <li>If the resulting document is a JSON document, extract the top-level <code>@context</code>
+ element using the JSON Pointer "/@context" as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-POINTER">JSON-POINTER</a></cite>]. Set <em>value</em>
+ to the extracted content, or an empty <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a> if no value exists.</li>
+ </ol>
+ </li>
+ <li>If <em>value</em> is a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>, perform the following steps:
+ <ol class="algorithm">
+ <li>
+ If <em>value</em> has a <code>@base</code> key, it <em class="rfc2119" title="must">must</em> have a value of a simple
+ <a class="tref internalDFN" title="string" href="#dfn-string">string</a> with the lexical form of an absolute IRI. Add the base mapping to the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local
+ context</a>. <p class="issue">Turtle allows @base to be relative. If we did this, we
+ would have to add <a href="#iri-expansion">IRI Expansion</a>.</p>
+ </li>
+ <li>
+ If <em>value</em> has a <code>@vocab</code> key, it <em class="rfc2119" title="must">must</em> have a value of a simple
+ <a class="tref internalDFN" title="string" href="#dfn-string">string</a> with the lexical form of an absolute IRI. Add the vocabulary mapping to the
+ <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> after performing <a href="#iri-expansion">IRI Expansion</a> on
+ the associated value.
+ </li>
+ <li>
+ If <em>value</em> has a <code>@coerce</code> key, it <em class="rfc2119" title="must">must</em> have a value of a
+ <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>. Add the <code>@coerce</code> mapping to the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>
+ performing <a href="#iri-expansion">IRI Expansion</a> on the associated value(s).
+ </li>
+ <li>
+ If <em>value</em> has a <code>@language</code> key, it <em class="rfc2119" title="must">must</em> have a value of a
+ simple <a class="tref internalDFN" title="string" href="#dfn-string">string</a> or <code>null</code>. Add the language to the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.
+ </li>
+ <li>
+ Otherwise, for each key in <em>value</em>having the lexical form of <cite><a href="http://www.w3.org/TR/2009/REC-xml-names-20091208/#NT-NCName">NCName</a></cite>, it's value
+ <em class="rfc2119" title="must">must</em> have be a simple <a class="tref internalDFN" title="string" href="#dfn-string">string</a> with the lexical form of IRI. Merge the key-value
+ pair into the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.
+ </li>
+ </ol>
+ </li>
+ <li>
+ Merge the of <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>'s <code>@coerce</code> mapping into the
+ <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>'s <code>@coerce</code> mapping as described <a href="#coerce">below</a>.
+ </li>
+ <li>
+ Merge all entries other than the <code>@coerce</code> mapping from the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> to the
+ <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> overwriting any duplicate values.
+ </li>
+ </ol>
+
+ <div class="section">
+ <h4 id="coerce">Coerce</h4>
+ <p>
+ Map each key-value pair in the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>'s
+ <code>@coerce</code> mapping into the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>'s
+ <code>@coerce</code> mapping, overwriting any duplicate values in
+ the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>'s <code>@coerce</code> mapping.
+ The <code>@coerce</code> mapping has either a single
+ <code>prefix:suffix</code> value, a single <a class="tref internalDFN" title="term" href="#dfn-term">term</a> value or an
+ <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of <code>prefix:suffix</code> or <a class="tref internalDFN" title="term" href="#dfn-term">term</a> values.
+ When merging with an existing mapping in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>,
+ map all <a class="tref internalDFN" title="term" href="#dfn-term">term</a> values to
+ <a class="tref internalDFN" title="array" href="#dfn-array">array</a> form and replace with the union of the value from
+ the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> and the value of the
+ <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>. If the result is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>
+ with a single value, the processor <em class="rfc2119" title="may">may</em> represent this as a string value.
+ </p>
+ </div>
+
+ <div class="section">
+ <h4 id="initial-context">Initial Context</h4>
+ <p>The <a class="tref internalDFN" title="initial_context" href="#dfn-initial_context">initial context</a> is initialized as follows:</p>
+ <ul>
+ <li>
+ <code>@base</code> is set using <cite><a href="http://www.ietf.org/rfc/rfc2396.txt">section 5.1 Establishing a
+ Base URI</a><a></a></cite><a> of [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3986">RFC3986</a></cite>]. Processors <em class="rfc2119" title="may">may</em> provide a means
+ of setting the base IRI programatically.
+ </a></li><a>
+ <li><code>@coerce</code> is set with a single mapping from <code>@iri</code> to <code>@type</code>.</li>
+ </a></ul><a>
+ <pre class="example">{
+ "@base": <span class="diff">document-location</span>,
+ "@coerce": {
+ "@iri": "@type"
+ }
+}</pre>
+ </a></div><a>
+</a></ol></div><a>
+
+<div class="section">
+ <h3 id="iri-expansion">IRI Expansion</h3>
+ <p>Keys and some values are evaluated to produce an IRI. This section defines an algorithm for
+ transforming a value representing an IRI into an actual IRI.</p>
+ <p>IRIs may be represented as an absolute IRI, a <a class="tref internalDFN" title="term" href="#dfn-term">term</a>, a <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>:suffix construct, or as a value relative to <code>@base</code>
+ or <code>@vocab</code>.</p>
+ <p>The algorithm for generating an IRI is:
+ </p><ol class="algorithm">
+ <li>Split the value into a <em>prefix</em> and <em>suffix</em> from the first occurrence of ':'.</li>
+ <li>If the prefix is a '_' (underscore), the IRI is unchanged.</li>
+ <li>If the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> contains a term mapping for <em>prefix</em>, generate an IRI
+ by prepending the mapped prefix to the (possibly empty) suffix using textual concatenation. Note that an empty
+ suffix and no suffix (meaning the value contains no ':' string at all) are treated equivalently.</li>
+ <li>If the IRI being processed is for a property (i.e., a key's value in a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>, or a
+ value in a <code>@coerce</code> mapping) and the active context has a <code>@vocab</code> mapping,
+ join the mapped value to the suffix using textual concatenation.</li>
+ <li>If the IRI being processed is for a subject or object (i.e., not a property) and the active context has a <code>@base</code> mapping,
+ join the mapped value to the suffix using the method described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3986">RFC3986</a></cite>].</li>
+ <li>Otherwise, use the value directly as an IRI.</li>
+ </ol>
+ <p></p>
+</div>
+
+<div class="section">
+ <h3 id="iri-compaction">IRI Compaction</h3>
+ <p>Some keys and values are expressed using IRIs. This section defines an
+ algorithm for transforming an IRI to a compact IRI using the
+ <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s specified in the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.</p>
+
+ <p>The algorithm for generating a compacted IRI is:
+ </p><ol class="algorithm">
+ <li>Search every key-value pair in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> for
+ a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> that is a complete match
+ against the IRI. If a complete match is found, the resulting compacted
+ IRI is the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> associated with the IRI in the
+ <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</li>
+ <li>If a complete match is not found, search for a partial match from
+ the beginning of the IRI. For all matches that are found, the resulting
+ compacted IRI is the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> associated with the partially
+ matched IRI in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> concatenated with a
+ colon (:) character and the unmatched part of the string. If there is
+ more than one compacted IRI produced, the final value is the
+ shortest and lexicographically least value of the entire set of compacted IRIs.</li>
+ </ol>
+ <p></p>
+</div>
+
+</a><div class="section"><a>
+ <h2 id="value-expansion">Value Expansion</h2>
+ <p>Some values in JSON-LD can be expressed in a compact form. These values
+ are required to be expanded at times when processing JSON-LD documents.
+ </p>
+
+ <p>The algorithm for expanding a value is:
+ </p></a><ol class="algorithm"><a>
+ </a><li><a>If the key that is associated with the value has an associated
+ coercion entry in the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>, the resulting
+ expansion is an object populated according to the following steps:
+ </a><ol class="algorithm"><a>
+ </a><li><a>If the coercion target is <code>@iri</code>, expand the value
+ by adding a new key-value pair where the key is <code>@iri</code>
+ and the value is the expanded IRI according to the
+ </a><a href="#iri-expansion">IRI Expansion</a> rules.</li>
+ <li>If the coercion target is a typed literal, expand the value
+ by adding two new key-value pairs. The first key-value pair
+ will be <code>@literal</code> and the unexpanded value. The second
+ key-value pair will be <code>@datatype</code> and the associated
+ coercion datatype expanded according to the
+ <a href="#iri-expansion">IRI Expansion</a> rules.</li>
+ </ol>
+ </li>
+ </ol>
+ <p></p>
+</div>
+
+<div id="value-compaction" class="section">
+ <h3><span class="secno">3.4 </span>Value Compaction</h3>
+ <p>Some values, such as IRIs and typed literals, may be expressed in an
+ expanded form in JSON-LD. These values are required to be compacted at
+ times when processing JSON-LD documents.
+ </p>
+
+ <p>The algorithm for compacting a value is:
+ </p><ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> contains a coercion target for the
+ key that is associated with the value, compact the value using the
+ following steps:
+ <ol class="algorithm">
+ <li>If the coercion target is an <code>@iri</code>, the compacted
+ value is the value associated with the <code>@iri</code> key,
+ processed according to the
+ <a href="#iri-compaction">IRI Compaction</a> steps.</li>
+ <li>If the coercion target is a typed literal, the compacted
+ value is the value associated with the <code>@literal</code> key.
+ </li>
+ <li>Otherwise, the value is not modified.</li>
+ </ol>
+ </li>
+ </ol>
+ <p></p>
+</div>
+
+<div id="expansion" class="section">
+<h3><span class="secno">3.5 </span>Expansion</h3>
+
+<p>Expansion is the process of taking a JSON-LD document and applying a
+context such that all IRI, datatypes, and literal values are expanded so
+that the context is no longer necessary. JSON-LD document expansion
+is typically used as a part of <a href="#normalization">Framing</a> or
+<a href="#normalization">Normalization</a>.</p>
+
+<p>For example, assume the following JSON-LD input document:</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "@coerce":
+ {
+ "@iri": "homepage"
+ }
+ },
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/"
+}</pre>
+
+<p>Running the JSON-LD Expansion algorithm against the JSON-LD input document
+provided above would result in the following output:</p>
+
+<pre class="example">{
+ "http://xmlns.com/foaf/0.1/name": "Manu Sporny",
+ "http://xmlns.com/foaf/0.1/homepage":
+ {
+ "@iri": "http://manu.sporny.org/"
+ }
+}</pre>
+
+<div id="expansion-algorithm" class="section">
+<h4><span class="secno">3.5.1 </span>Expansion Algorithm</h4>
+
+<p class="issue">This algorithm is a work in progress, do not implement it.</p>
+
+<ol class="algorithm">
+ <li>If the top-level item in the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>,
+ process each item in the <a class="tref internalDFN" title="array" href="#dfn-array">array</a> recursively using this algorithm.</li>
+ <li>If the top-level item in the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> is an object,
+ update the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> according to the steps outlined in
+ the <a href="#context">context</a> section. Process each key, expanding
+ the key according to the <a href="#iri-expansion">IRI Expansion</a> rules.</li>
+ <ol class="algorithm">
+ <li>Process each value associated with each key:
+ <ol class="algorithm">
+ <li>If the value is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, process each item in the <a class="tref internalDFN" title="array" href="#dfn-array">array</a>
+ recursively using this algorithm.</li>
+ <li>If the value is an object, process the object recursively
+ using this algorithm.</li>
+ <li>Otherwise, check to see the associated key has an associated
+ coercion rule. If the value should be coerced, expand the value
+ according to the <a href="#value-expansion">Value Expansion</a> rules.
+ If the value does not need to be coerced, leave the value as-is.
+ </li>
+ </ol>
+ </li><li>Remove the context from the object.</li>
+ </ol>
+</ol>
+</div>
+
+<p class="issue">What are the implications for expanding lists?</p>
+
+</div>
+
+<div id="compaction" class="section">
+<h3><span class="secno">3.6 </span>Compaction</h3>
+
+<p>Compaction is the process of taking a JSON-LD document and applying a
+context such that the most compact form of the document is generated. JSON
+is typically expressed in a very compact, key-value format. That is, full
+IRIs are rarely used as keys. At times, a JSON-LD document may be received
+that is not in its most compact form. JSON-LD, via the API, provides a way
+to compact a JSON-LD document.
+</p>
+
+<p>For example, assume the following JSON-LD input document:</p>
+
+<pre class="example">{
+ "http://xmlns.com/foaf/0.1/name": "Manu Sporny",
+ "http://xmlns.com/foaf/0.1/homepage":
+ {
+ "@iri": "http://manu.sporny.org/"
+ }
+}</pre>
+
+<p>Additionally, assume the following developer-supplied JSON-LD context:</p>
+
+<pre class="example">{
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "@coerce":
+ {
+ "@iri": "homepage"
+ }
+}</pre>
+
+<p>Running the JSON-LD Compaction algorithm given the context supplied above
+against the JSON-LD input document provided above would result in the following
+output:</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "@coerce":
+ {
+ "@iri": "homepage"
+ }
+ },
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/"
+}</pre>
+
+<p>The compaction algorithm also enables the developer to map any expanded
+format into an application-specific compacted format. While the context
+provided above mapped <code>http://xmlns.com/foaf/0.1/name</code> to
+<strong>name</strong>, it could have also mapped it to any arbitrary string
+provided by the developer.
+</p>
+
+<div id="compaction-algorithm" class="section">
+<h4><span class="secno">3.6.1 </span>Compaction Algorithm</h4>
+
+<p class="issue">This algorithm is a work in progress, do not implement it.</p>
+
+<ol class="algorithm">
+ <li>Perform the <a href="#expansion-algorithm">Expansion Algorithm</a> on
+ the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a>. This removes any existing context to allow the given context to be cleanly applied.</li>
+ <li>Set the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> to the given context.
+ </li><li>If the top-level item is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, process each item in the <a class="tref internalDFN" title="array" href="#dfn-array">array</a>
+ recursively, starting at this step.
+ </li><li>If the top-level item is an object, compress each key using the steps
+ defined in <a href="#iri-compaction">IRI Compaction</a> and compress each
+ value using the steps defined in
+ <a href="#value-compaction">Value Compaction</a>.</li>
+
+</ol>
+</div>
+
+<p class="issue">What are the implications for compacting lists?</p>
+
+</div>
+
+
+<div id="framing" class="section">
+<h3><span class="secno">3.7 </span>Framing</h3>
+
+<p>JSON-LD Framing allows developers to query by example and
+force a specific tree layout to a JSON-LD document.
+</p>
+
+<p>A JSON-LD document is a representation of a directed graph. A single
+directed graph can have many different serializations, each expressing
+exactly the same information. Developers typically work with trees, represented as
+<a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>s. While mapping a graph to
+a tree can be done, the layout of the end result must be specified in advance.
+A <dfn title="frame" id="dfn-frame">Frame</dfn> can be used by a developer on a JSON-LD document to
+specify a deterministic layout for a graph.
+</p>
+
+<p>Framing is the process of taking a JSON-LD document, which expresses a
+graph of information, and applying a specific graph layout
+(called a <a class="tref internalDFN" title="frame" href="#dfn-frame">Frame</a>).
+</p>
+
+<p>The JSON-LD document below expresses a library, a book and a chapter:</p>
+
+<pre class="example">{
+ "@context": {
+ "Book": "http://example.org/vocab#Book",
+ "Chapter": "http://example.org/vocab#Chapter",
+ "contains": "http://example.org/vocab#contains",
+ "creator": "http://purl.org/dc/terms/creator"
+ "description": "http://purl.org/dc/terms/description"
+ "Library": "http://example.org/vocab#Library",
+ "title": "http://purl.org/dc/terms/title",
+ "@coerce":
+ {
+ "@iri": "contains"
+ },
+ },
+ "@subject":
+ [{
+ "@subject": "http://example.com/library",
+ "@type": "Library",
+ "contains": "http://example.org/library/the-republic"
+ },
+ {
+ "@subject": "http://example.org/library/the-republic",
+ "@type": "Book",
+ "creator": "Plato",
+ "title": "The Republic",
+ "contains": "http://example.org/library/the-republic#introduction"
+ },
+ {
+ "@subject": "http://example.org/library/the-republic#introduction",
+ "@type": "Chapter",
+ "description": "An introductory chapter on The Republic.",
+ "title": "The Introduction"
+ }]
+}</pre>
+
+<p>Developers typically like to operate on items in a hierarchical, tree-based
+fashion. Ideally, a developer would want the data above sorted into top-level
+libraries, then the books that are contained in each library, and then the
+chapters contained in each book. To achieve that layout, the developer can
+define the following <a class="tref internalDFN" title="frame" href="#dfn-frame">frame</a>:</p>
+
+<pre class="example">{
+ "@context": {
+ "Book": "http://example.org/vocab#Book",
+ "Chapter": "http://example.org/vocab#Chapter",
+ "contains": "http://example.org/vocab#contains",
+ "creator": "http://purl.org/dc/terms/creator"
+ "description": "http://purl.org/dc/terms/description"
+ "Library": "http://example.org/vocab#Library",
+ "title": "http://purl.org/dc/terms/title"
+ },
+ "@type": "Library",
+ "contains": {
+ "@type": "Book",
+ "contains": {
+ "@type": "Chapter"
+ }
+ }
+}</pre>
+
+<p>When the framing algorithm is run against the previously defined
+JSON-LD document, paired with the <a class="tref internalDFN" title="frame" href="#dfn-frame">frame</a> above, the following
+JSON-LD document is the end result:</p>
+
+<pre class="example">{
+ "@context": {
+ "Book": "http://example.org/vocab#Book",
+ "Chapter": "http://example.org/vocab#Chapter",
+ "contains": "http://example.org/vocab#contains",
+ "creator": "http://purl.org/dc/terms/creator"
+ "description": "http://purl.org/dc/terms/description"
+ "Library": "http://example.org/vocab#Library",
+ "title": "http://purl.org/dc/terms/title"
+ },
+ "@subject": "http://example.org/library",
+ "@type": "Library",
+ "contains": {
+ <span class="diff">"@subject": "http://example.org/library/the-republic",</span>
+ "@type": "Book",
+ <span class="diff">"creator": "Plato",</span>
+ <span class="diff">"title": "The Republic",</span>
+ "contains": {
+ <span class="diff">"@subject": "http://example.org/library/the-republic#introduction",</span>
+ "@type": "Chapter",
+ <span class="diff">"description": "An introductory chapter on The Republic.",</span>
+ <span class="diff">"title": "The Introduction"</span>
+ },
+ },
+}</pre>
+
+<div id="framing-algorithm-terms" class="section">
+<h4><span class="secno">3.7.1 </span>Framing Algorithm Terms</h4>
+<p class="issue">This algorithm is a work in progress, do not implement it.</p>
+
+ <dl>
+ <dt><dfn title="input_frame" id="dfn-input_frame">input frame</dfn></dt>
+ <dd>
+ the initial <a class="tref internalDFN" title="frame" href="#dfn-frame">frame</a> provided to the framing algorithm.
+ </dd>
+ <dt><dfn title="framing_context" id="dfn-framing_context">framing context</dfn></dt>
+ <dd>
+ a context containing the <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a>, the
+ <a class="tref internalDFN" title="explicit_inclusion_flag" href="#dfn-explicit_inclusion_flag">explicit inclusion flag</a> and the
+ <a class="tref internalDFN" title="omit_default_flag" href="#dfn-omit_default_flag">omit default flag</a>.
+ </dd>
+ <dt><dfn title="object_embed_flag" id="dfn-object_embed_flag">object embed flag</dfn></dt>
+ <dd>
+ a flag specifying that objects should be directly embedded in the output,
+ instead of being referred to by their IRI.
+ </dd>
+ <dt><dfn title="explicit_inclusion_flag" id="dfn-explicit_inclusion_flag">explicit inclusion flag</dfn></dt>
+ <dd>
+ a flag specifying that for properties to be included in the output, they
+ must be explicitly declared in the <a class="tref internalDFN" title="framing_context" href="#dfn-framing_context">framing context</a>.
+ </dd>
+ <dt><dfn title="omit_missing_properties_flag" id="dfn-omit_missing_properties_flag">omit missing properties flag</dfn></dt>
+ <dd>
+ a flag specifying that properties that are missing from the
+ <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> should be omitted from the output.
+ </dd>
+ <dt><dfn title="omit_default_flag" id="dfn-omit_default_flag">omit default flag</dfn></dt>
+ <dd class="issue">
+ Referenced from <a class="tref internalDFN" title="framing_context" href="#dfn-framing_context">framing context</a>, but not defined
+ </dd>
+ <dt><dfn title="match_limit" id="dfn-match_limit">match limit</dfn></dt>
+ <dd>
+ A value specifying the maximum number of matches to accept when building
+ arrays of values during the framing algorithm. A value of -1 specifies
+ that there is no match limit.
+ </dd>
+ <dt><dfn title="map_of_embedded_subjects" id="dfn-map_of_embedded_subjects">map of embedded subjects</dfn></dt>
+ <dd>
+ A map that tracks if a subject has been embedded in the output of the
+ <a href="#framing-algorithm">Framing Algorithm</a>.
+ </dd>
+ </dl>
+</div>
+
+<div id="framing-algorithm" class="section">
+<h4><span class="secno">3.7.2 </span>Framing Algorithm</h4>
+
+<p>The framing algorithm takes <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> that has been
+normalized according to the
+<a href="#normalization-algorithm">Normalization Algorithm</a>
+(<strong>normalized input</strong>), an
+<a class="tref internalDFN" title="input_frame" href="#dfn-input_frame">input frame</a> that has been expanded according to the
+<a href="#expansion-algorithm">Expansion Algorithm</a>
+(<strong>expanded frame</strong>), and a number of options and produces
+<a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a>. The following series of steps is the recursive
+portion of the framing algorithm:
+</p>
+
+<ol class="algorithm">
+ <li>Initialize the <a class="tref internalDFN" title="framing_context" href="#dfn-framing_context">framing context</a> by setting the
+ <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a>, clearing the
+ <a class="tref internalDFN" title="explicit_inclusion_flag" href="#dfn-explicit_inclusion_flag">explicit inclusion flag</a>, and clearing the
+ <a class="tref internalDFN" title="omit_missing_properties_flag" href="#dfn-omit_missing_properties_flag">omit missing properties flag</a>. Override these values
+ based on input options provided to the algorithm by the application.
+ </li>
+ <li>Generate a <dfn title="list_of_frames" id="dfn-list_of_frames">list of frames</dfn> by processing the
+ <strong>expanded frame</strong>:
+ <ol class="algorithm">
+ <li>If the <strong>expanded frame</strong> is not an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, set
+ <a class="tref internalDFN" title="match_limit" href="#dfn-match_limit">match limit</a> to 1, place the
+ <strong>expanded frame</strong> into the <a class="tref internalDFN" title="list_of_frames" href="#dfn-list_of_frames">list of frames</a>,
+ and set the <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a> to <code>null</code>.</li>
+ <li>If the <strong>expanded frame</strong> is an empty <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, place an
+ empty object into the <a class="tref internalDFN" title="list_of_frames" href="#dfn-list_of_frames">list of frames</a>,
+ set the <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a> to an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, and set
+ <a class="tref internalDFN" title="match_limit" href="#dfn-match_limit">match limit</a> to -1.</li>
+ <li>If the <strong>expanded frame</strong> is a non-empty <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, add
+ each item in the <strong>expanded frame</strong> into the
+ <a class="tref internalDFN" title="list_of_frames" href="#dfn-list_of_frames">list of frames</a>, set the <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a> to an
+ <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, and set <a class="tref internalDFN" title="match_limit" href="#dfn-match_limit">match limit</a> to -1.</li>
+ </ol></li>
+ <li>Create a <dfn title="match_array" id="dfn-match_array">match array</dfn> for each <strong>expanded frame</strong>
+ in the <a class="tref internalDFN" title="list_of_frames" href="#dfn-list_of_frames">list of frames</a> halting when either the
+ <a class="tref internalDFN" title="match_limit" href="#dfn-match_limit">match limit</a> is zero or the end of the
+ <a class="tref internalDFN" title="list_of_frames" href="#dfn-list_of_frames">list of frames</a> is reached. If an
+ <strong>expanded frame</strong> is
+ not an object, the processor <em class="rfc2119" title="must">must</em> throw a <code>Invalid Frame Format</code>
+ exception. Add each matching item from the <strong>normalized input</strong>
+ to the <a class="tref internalDFN" title="matches_array" href="#dfn-matches_array">matches array</a> and decrement the
+ <a class="tref internalDFN" title="match_limit" href="#dfn-match_limit">match limit</a> by 1 if:
+ <ol class="algorithm">
+ <li>The <strong>expanded frame</strong> has an <code>rdf:type</code>
+ that exists in the item's list of <code>rdf:type</code>s. Note:
+ the <code>rdf:type</code> can be an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, but only one value needs
+ to be in common between the item and the
+ <strong>expanded frame</strong> for a match.</li>
+ <li>The <strong>expanded frame</strong> does not have an
+ <code>rdf:type</code> property, but every property in the
+ <strong>expanded frame</strong> exists in the item.</li>
+ </ol>
+ <p class="issue"><dfn title="matches_array" id="dfn-matches_array">matches array</dfn> not defined anywhere.</p></li>
+ <li>Process each item in the <a class="tref internalDFN" title="match_array" href="#dfn-match_array">match array</a> with its associated
+ <dfn title="match_frame" id="dfn-match_frame">match frame</dfn>:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a> contains an <code>@embed</code>
+ keyword, set the <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a> to its value.
+ If the <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a> contains an <code>@explicit</code>
+ keyword, set the <a class="tref internalDFN" title="explicit_inclusion_flag" href="#dfn-explicit_inclusion_flag">explicit inclusion flag</a> to its value.
+ Note: if the keyword exists, but the value is neither
+ <code>true</code> or <code>false</code>, set the associated flag to
+ <code>true</code>.</li>
+ <li>If the <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a> is cleared and the item has
+ the <code>@subject</code> property, replace the item with the value
+ of the <code>@subject</code> property.</li>
+ <li>If the <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a> is set and the item has
+ the <code>@subject</code> property, and its IRI is in the
+ <a class="tref internalDFN" title="map_of_embedded_subjects" href="#dfn-map_of_embedded_subjects">map of embedded subjects</a>, throw a
+ <code>Duplicate Embed</code> exception.</li>
+ <li>If the <a class="tref internalDFN" title="object_embed_flag" href="#dfn-object_embed_flag">object embed flag</a> is set and the item has
+ the <code>@subject</code> property and its IRI is not in the
+ <a class="tref internalDFN" title="map_of_embedded_subjects" href="#dfn-map_of_embedded_subjects">map of embedded subjects</a>:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="explicit_inclusion_flag" href="#dfn-explicit_inclusion_flag">explicit inclusion flag</a> is set,
+ then delete any key from the item that does not exist in the
+ <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a>, except <code>@subject</code>.</li>
+ <li>For each key in the <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a>, except for
+ keywords and <code>rdf:type</code>:
+ <ol class="algorithm">
+ <li>If the key is in the item, then build a new
+ <dfn title="recursion_input_list" id="dfn-recursion_input_list">recursion input list</dfn> using the object or objects
+ associated with the key. If any object contains an
+ <code>@iri</code> value that exists in the
+ <strong>normalized input</strong>, replace the object in the
+ <a class="tref internalDFN" title="recursion_input_list" href="#dfn-recursion_input_list">recursion input list</a> with a new object containing
+ the <code>@subject</code> key where the value is the value of
+ the <code>@iri</code>, and all of the other key-value pairs for
+ that subject. Set the <dfn title="recursion_match_frame" id="dfn-recursion_match_frame">recursion match frame</dfn> to the
+ value associated with the <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a>'s key. Replace
+ the value associated with the key by recursively calling this
+ algorithm using <a class="tref internalDFN" title="recursion_input_list" href="#dfn-recursion_input_list">recursion input list</a>,
+ <a class="tref internalDFN" title="recursion_match_frame" href="#dfn-recursion_match_frame">recursion match frame</a> as input.</li>
+ <li>If the key is not in the item, add the key to the item and
+ set the associated value to an empty array if the
+ <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a> key's value is an array
+ or <code>null</code> otherwise.</li>
+ <li>If value associated with the item's key is <code>null</code>,
+ process the <a class="tref internalDFN" title="omit_missing_properties_flag" href="#dfn-omit_missing_properties_flag">omit missing properties flag</a>:
+ <ol class="algorithm">
+ <li>If the value associated with the key in the
+ <a class="tref internalDFN" title="match_frame" href="#dfn-match_frame">match frame</a> is an array, use the first frame
+ from the array as the <dfn title="property_frame" id="dfn-property_frame">property frame</dfn>, otherwise
+ set the <a class="tref internalDFN" title="property_frame" href="#dfn-property_frame">property frame</a> to an empty object.</li>
+ <li>If the <a class="tref internalDFN" title="property_frame" href="#dfn-property_frame">property frame</a> contains an
+ <code>@omitDefault</code> keyword, set the
+ <a class="tref internalDFN" title="omit_missing_properties_flag" href="#dfn-omit_missing_properties_flag">omit missing properties flag</a> to its value.
+ Note: if the keyword exists, but the value is neither
+ <code>true</code> or <code>false</code>, set the associated
+ flag to <code>true</code>.</li>
+ <li>If the <a class="tref internalDFN" title="omit_missing_properties_flag" href="#dfn-omit_missing_properties_flag">omit missing properties flag</a> is set,
+ delete the key in the item. Otherwise, if the
+ <code>@default</code> keyword is set in the
+ <a class="tref internalDFN" title="property_frame" href="#dfn-property_frame">property frame</a> set the item's value to the value
+ of <code>@default</code>.</li>
+ </ol></li>
+ </ol></li>
+ </ol>
+ </li><li>If the <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a> is <code>null</code> set it to
+ the item, otherwise, append the item to the
+ <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a>.
+ </li></ol>
+ </li><li>Return the <a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a>.</li>
+</ol>
+
+The final, non-recursive step of the framing algorithm requires the
+<a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a> to be compacted according to the
+<a href="#compaction-algorithm">Compaction Algorithm</a> by using the
+context provided in the <a class="tref internalDFN" title="input_frame" href="#dfn-input_frame">input frame</a>. The resulting value is the
+final output of the compaction algorithm and is what should be returned to the
+application.
+
+</div>
+
+<p class="issue">What are the implications for framing lists?</p>
+
+</div>
+
+<div id="normalization" class="section">
+<h3><span class="secno">3.8 </span>Normalization</h3>
+
+<p class="issue">This algorithm is a work in progress, do not implement it.</p>
+
+<p>Normalization is the process of taking <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> and
+performing a deterministic transformation on that input that results in all
+aspects of the graph being fully expanded and named in the
+<a class="tref internalDFN" title="json-ld_output" href="#dfn-json-ld_output">JSON-LD output</a>. The normalized output is generated in such a way
+that any conforming JSON-LD processor will generate identical output
+given the same input. The problem is a fairly difficult technical
+problem to solve because it requires a directed graph to be ordered into a
+set of nodes and edges in a deterministic way. This is easy to do when all of
+the nodes have unique names, but very difficult to do when some of the nodes
+are not labeled.
+</p>
+
+<p>Normalization is useful when comparing two graphs against one another,
+when generating a detailed list of differences between two graphs, and
+when generating a cryptographic digital signature for information contained
+in a graph or when generating a hash of the information contained in a graph.
+</p>
+
+<p>The example below is an un-normalized JSON-LD document:</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "xsd": "http://www.w3.org/2001/XMLSchema#",
+ "@coerce":
+ {
+ "@iri": ["homepage"]
+ }
+ },
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/"
+}</pre>
+
+<p>The example below is the normalized form of the JSON-LD document above:</p>
+
+<p class="note">Whitespace is used below to aid readability. The normalization
+algorithm for JSON-LD removes all unnecessary whitespace in the fully
+normalized form.</p>
+
+<pre class="example">[{
+ "@subject":
+ {
+ "@iri": "_:c14n0"
+ },
+ "http://xmlns.com/foaf/0.1/homepage":
+ {
+ "@iri": "http://manu.sporny.org/"
+ },
+ "http://xmlns.com/foaf/0.1/name": "Manu Sporny"
+}]</pre>
+
+<p>Notice how all of the <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s have been expanded and sorted in
+alphabetical order. Also, notice how the <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> has been
+labeled with a <dfn title="blank_node_identifier" id="dfn-blank_node_identifier">blank node identifier</dfn>. Normalization ensures that any arbitrary
+graph containing exactly the same information would be normalized to exactly
+the same form shown above.</p>
+
+<p>In time, there may be more than one normalization algorithm that will need
+to be identified. For identification purposes, this algorithm is named
+"Universal Graph Normalization Algorithm 2011"
+(<abbr title="Universal Graph Normalization Algorithm 2011">UGNA2011</abbr>).
+</p>
+
+<div id="normalization-algorithm-terms" class="section">
+<h4><span class="secno">3.8.1 </span>Normalization Algorithm Terms</h4>
+ <dl>
+ <dt><dfn title="label" id="dfn-label">label</dfn></dt>
+ <dd>
+ The subject <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> associated with a graph node. The subject IRI is expressed
+ using a key-value pair in a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> where the key is
+ <code>@subject</code> and the value is a string that is an IRI or
+ a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> containing the key <code>@iri</code> and
+ a value that is a string that is an IRI.
+ </dd>
+ <dt><dfn title="list_of_expanded_nodes" id="dfn-list_of_expanded_nodes">list of expanded nodes</dfn></dt>
+ <dd>
+ A list of all nodes in the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> graph containing no
+ embedded objects and having all keys and values expanded according to the
+ steps in the <a href="#expansion-algorithm">Expansion Algorithm</a>.
+ </dd>
+ <dt><dfn title="alpha" id="dfn-alpha">alpha</dfn> and <dfn title="beta" id="dfn-beta">beta</dfn> values</dt>
+ <dd>
+ The words <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a> refer to the first and
+ second nodes or values being examined in an algorithm. The names are
+ merely used to refer to each input value to a comparison algorithm.
+ </dd>
+ <dt><dfn title="renaming_counter" id="dfn-renaming_counter">renaming counter</dfn></dt>
+ <dd>
+ A counter that is used during the
+ <a href="#node-relabeling-algorithm">Node Relabeling Algorithm</a>. The
+ counter typically starts at one (1) and counts up for every node that is
+ relabeled. There will be two such renaming counters in an implementation
+ of the normalization algorithm. The first is the
+ <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a> and the second is the
+ <a class="tref internalDFN" title="deterministic_labeling_counter" href="#dfn-deterministic_labeling_counter">deterministic labeling counter</a>.
+ </dd>
+ <dt><dfn title="serialization_label" id="dfn-serialization_label">serialization label</dfn></dt>
+ <dd>
+ An identifier that is created to aid in the normalization process in the
+ <a href="#deep-comparison-algorithm">Deep Comparison Algorithm</a>. The
+ value typically takes the form of <code>s<NUMBER></code> or
+ <code>c<NUMBER></code>.
+ </dd>
+</dl>
+</div>
+
+<div id="normalization-state" class="section">
+<h4><span class="secno">3.8.2 </span>Normalization State</h4>
+
+<p>When performing the steps required by the normalization algorithm,
+it is helpful to track the many pieces of information in a
+data structure called the <dfn title="normalization_state" id="dfn-normalization_state">normalization state</dfn>. Many of these
+pieces simply provide indexes into the graph. The information
+contained in the <a class="tref internalDFN" title="normalization_state" href="#dfn-normalization_state">normalization state</a> is described below.</p>
+
+<dl>
+ <dt><dfn title="node_state" id="dfn-node_state">node state</dfn></dt>
+ <dd>
+ Each node in the graph will be assigned a <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>. This
+ state contains the information necessary to deterministically
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a> all nodes in the graph. A <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>
+ includes:
+ <dl>
+ <dt><dfn title="node_reference" id="dfn-node_reference">node reference</dfn></dt>
+ <dd>
+ A <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> is a reference to a node in the graph.
+ For a given <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, its <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>
+ refers to the node that the state is for. When a
+ <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a> is created, its <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>
+ should be to the node it is created for.
+ </dd>
+ <dt><dfn title="outgoing_list" id="dfn-outgoing_list">outgoing list</dfn></dt>
+ <dd>
+ Lists the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s for all nodes that are properties of
+ the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>. This list should be initialized
+ by iterating over every object associated with a property in the
+ <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> adding its label if it is another node.
+ </dd>
+ <dt><dfn title="incoming_list" id="dfn-incoming_list">incoming list</dfn></dt>
+ <dd>
+ Lists the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s for all nodes in the graph for which
+ the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> is a property. This list is
+ initialized to an empty list.
+ </dd>
+ <dt><dfn title="outgoing_serialization_map" id="dfn-outgoing_serialization_map">outgoing serialization map</dfn></dt>
+ <dd>
+ Maps node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s to <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s.
+ This map is initialized to an empty map. When this map is populated,
+ it will be filled with keys that are the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s of every node in the
+ graph with a label that begins with <code>_:</code> and that has a
+ path, via properties, that starts with the
+ <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>.
+ </dd>
+ <dt><dfn title="outgoing_serialization" id="dfn-outgoing_serialization">outgoing serialization</dfn></dt>
+ <dd>
+ A string that can be lexicographically compared to the
+ <a class="tref internalDFN" title="outgoing_serialization" href="#dfn-outgoing_serialization">outgoing serialization</a>s of other
+ <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>s. It is a representation of the
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a> and other related
+ information. This string is initialized to an empty string.
+ </dd>
+ <dt><dfn title="incoming_serialization_map" id="dfn-incoming_serialization_map">incoming serialization map</dfn></dt>
+ <dd>
+ Maps node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s to <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s.
+ This map is initialized to an empty map. When this map is populated,
+ it will be filled with keys that are the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s of every
+ node in the graph with a <a class="tref internalDFN" title="label" href="#dfn-label">label</a> that begins with
+ <code>_:</code> and that has a path, via properties, that ends with
+ the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>.
+ </dd>
+ <dt><dfn title="incoming_serialization" id="dfn-incoming_serialization">incoming serialization</dfn></dt>
+ <dd>
+ A string that can be lexicographically compared to the
+ <a class="tref internalDFN" title="outgoing_serialization" href="#dfn-outgoing_serialization">outgoing serialization</a>s of other
+ <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>s. It is a representation of the
+ <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a> and other related
+ information. This string is initialized to an empty string.
+ </dd>
+ </dl>
+ </dd>
+ <dt><dfn title="node_state_map" id="dfn-node_state_map">node state map</dfn></dt>
+ <dd>
+ A mapping from a node's <a class="tref internalDFN" title="label" href="#dfn-label">label</a> to a <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>.
+ It is initialized to an empty map.
+ </dd>
+ <dt><dfn title="labeling_prefix" id="dfn-labeling_prefix">labeling prefix</dfn></dt>
+ <dd>
+ The labeling prefix is a string that is used as the beginning of a node
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a>. It should be initialized to a random base string that
+ starts with the characters <code>_:</code>, is not used by any other
+ node's <a class="tref internalDFN" title="label" href="#dfn-label">label</a> in the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a>, and does not
+ start with the characters <code>_:c14n</code>. The prefix has two uses.
+ First it is used to temporarily name nodes during the normalization
+ algorithm in a way that doesn't collide with the names that already
+ exist as well as the names that will be generated by the normalization
+ algorithm. Second, it will eventually be set to <code>_:c14n</code> to
+ generate the final, deterministic labels for nodes in the graph. This
+ prefix will be concatenated with the <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a> to
+ produce a node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>. For example, <code>_:j8r3k</code> is
+ a proper initial value for the <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a>.
+ </dd>
+ <dt><dfn title="labeling_counter" id="dfn-labeling_counter">labeling counter</dfn></dt>
+ <dd>
+ A counter that is used to label nodes. It is appended to the
+ <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a> to create a node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>. It is
+ initialized to <code>1</code>.
+ </dd>
+ <dt><dfn title="deterministic_labeling_counter" id="dfn-deterministic_labeling_counter">deterministic labeling counter</dfn></dt>
+ <dd class="issue">
+ Not defined.
+ </dd>
+ <dt><dfn title="map_of_flattened_nodes" id="dfn-map_of_flattened_nodes">map of flattened nodes</dfn></dt>
+ <dd>
+ A map containing a representation of all nodes in the graph where the
+ key is a node <a class="tref internalDFN" title="label" href="#dfn-label">label</a> and the value is a single
+ <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that has no nested sub-objects
+ and has had all properties for the same node merged into a single
+ <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>.
+ </dd>
+</dl>
+
+</div>
+
+<div id="normalization-algorithm" class="section">
+<h4><span class="secno">3.8.3 </span>Normalization Algorithm</h4>
+
+<p>The normalization algorithm expands the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a>,
+flattens the data structure, and creates an initial set of names for all
+nodes in the graph. The flattened data structure is then processed by a
+node labeling algorithm in order to get a fully expanded and named list of
+nodes which is then sorted. The result is a deterministically named and
+ordered list of graph nodes.
+</p>
+
+<ol class="algorithm">
+<li>Expand the <a class="tref internalDFN" title="json-ld_input" href="#dfn-json-ld_input">JSON-LD input</a> according to the steps in
+the <a href="#expansion-algorithm">Expansion Algorithm</a> and store the
+result as the <strong>expanded input</strong>.</li>
+<li>Create a <a class="tref internalDFN" title="normalization_state" href="#dfn-normalization_state">normalization state</a>.</li>
+<li>Initialize the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a> by recursively
+processing every <dfn title="expanded_node" id="dfn-expanded_node">expanded node</dfn> in the
+<strong>expanded input</strong> in depth-first order:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a> is an unlabeled node, add a
+ new key-value pair to the <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a>
+ where the key is <code>@subject</code> and the value is the
+ concatenation of the <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a>
+ and the string value of the <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a>.
+ Increment the <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a>.</li>
+ <li>Add the <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a> to the
+ <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a>:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a>'s <a class="tref internalDFN" title="label" href="#dfn-label">label</a> is already
+ in the
+ <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a> merge all properties from the
+ entry in the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a> into the
+ <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a>.</li>
+ <li>Go through every property associated with an array in the
+ <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a> and remove any duplicate <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> entries from
+ the array. If the resulting array only has one IRI entry, change it
+ from an array to an object.</li>
+ <li>Set the entry for the <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a>'s <a class="tref internalDFN" title="label" href="#dfn-label">label</a>
+ in the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a> to the
+ <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a>.
+ </li></ol></li>
+ <li>After exiting the recursive step, replace the reference to the
+ <a class="tref internalDFN" title="expanded_node" href="#dfn-expanded_node">expanded node</a> with an object containing a single
+ key-value pair where the key is <code>@iri</code> and the value is
+ the value of the <code>@subject</code> key in the node.</li>
+ </ol></li>
+<li>For every entry in the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a>, insert a
+ key-value pair into the <a class="tref internalDFN" title="node_state_map" href="#dfn-node_state_map">node state map</a> where the key is the
+ key from the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a> and the value is a
+ <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a> where its <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> refers to
+ the value from the <a class="tref internalDFN" title="map_of_flattened_nodes" href="#dfn-map_of_flattened_nodes">map of flattened nodes</a>.
+</li><li>Populate the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a> for each <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>
+ by iterating over every node in the graph and adding its <a class="tref internalDFN" title="label" href="#dfn-label">label</a>
+ to the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a> associated with each node found in its
+ properties.</li>
+<li>For every entry in the <a class="tref internalDFN" title="node_state_map" href="#dfn-node_state_map">node state map</a> that has a
+<a class="tref internalDFN" title="label" href="#dfn-label">label</a> that begins with <code>_:c14n</code>, relabel the node
+using the <a href="#node-relabeling-algorithm">Node Relabeling Algorithm</a>.
+</li><li>Label all of the nodes that contain a <code>@subject</code> key associated
+with a value starting with <code>_:</code> according to the steps in the
+<a href="#deterministic-labeling-algorithm">Deterministic Labeling Algorithm</a>.
+</li>
+</ol>
+</div>
+
+<div id="node-relabeling-algorithm" class="section">
+<h4><span class="secno">3.8.4 </span>Node Relabeling Algorithm</h4>
+
+<p>This algorithm renames a node by generating a unique
+<dfn title="new_label" id="dfn-new_label">new label</dfn> and updating all references to that <a class="tref internalDFN" title="label" href="#dfn-label">label</a>
+in the <a class="tref internalDFN" title="node_state_map" href="#dfn-node_state_map">node state map</a>. The <dfn title="old_label" id="dfn-old_label">old label</dfn> and the
+<a class="tref internalDFN" title="normalization_state" href="#dfn-normalization_state">normalization state</a> must be given as an input to the
+algorithm. The <a class="tref internalDFN" title="old_label" href="#dfn-old_label">old label</a> is the current <a class="tref internalDFN" title="label" href="#dfn-label">label</a> of
+the node that is to be relabeled.
+
+</p><p>The node relabeling algorithm is as follows:</p>
+
+<ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a> is <code>_:c14n</code> and the
+ <a class="tref internalDFN" title="old_label" href="#dfn-old_label">old label</a> begins with <code>_:c14n</code> then return as
+ the node has already been renamed.
+ </li>
+ <li>Generate the <a class="tref internalDFN" title="new_label" href="#dfn-new_label">new label</a> by concatenating the
+ <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a> with the string value of the
+ <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a>. Increment the <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a>.
+ </li>
+ <li>For the <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a> associated with the
+ <a class="tref internalDFN" title="old_label" href="#dfn-old_label">old label</a>, update every node in the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a>
+ by changing all the properties that reference the <a class="tref internalDFN" title="old_label" href="#dfn-old_label">old label</a> to
+ the <a class="tref internalDFN" title="new_label" href="#dfn-new_label">new label</a>.
+ </li>
+ <li>Change the <a class="tref internalDFN" title="old_label" href="#dfn-old_label">old label</a> key in the <a class="tref internalDFN" title="node_state_map" href="#dfn-node_state_map">node state map</a>
+ to the <a class="tref internalDFN" title="new_label" href="#dfn-new_label">new label</a> and set the associated
+ <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>'s <a class="tref internalDFN" title="label" href="#dfn-label">label</a> to the
+ <a class="tref internalDFN" title="new_label" href="#dfn-new_label">new label</a>.
+ </li>
+</ol>
+</div>
+
+<div id="deterministic-labeling-algorithm" class="section">
+<h4><span class="secno">3.8.5 </span>Deterministic Labeling Algorithm</h4>
+
+<p>The deterministic labeling algorithm takes the
+<a class="tref internalDFN" title="normalization_state" href="#dfn-normalization_state">normalization state</a>
+and produces a <dfn title="list_of_finished_nodes" id="dfn-list_of_finished_nodes">list of finished nodes</dfn> that is sorted and
+contains deterministically named and expanded nodes from the graph.
+
+</p><ol class="algorithm">
+ <li>Set the <a class="tref internalDFN" title="labeling_prefix" href="#dfn-labeling_prefix">labeling prefix</a> to <code>_:c14n</code>, the
+ <a class="tref internalDFN" title="labeling_counter" href="#dfn-labeling_counter">labeling counter</a> to <code>1</code>,
+ the <a class="tref internalDFN" title="list_of_finished_nodes" href="#dfn-list_of_finished_nodes">list of finished nodes</a> to an empty array, and create
+ an empty array, the <dfn title="list_of_unfinished_nodes" id="dfn-list_of_unfinished_nodes">list of unfinished nodes</dfn>.</li>
+ <li>For each <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> in the <a class="tref internalDFN" title="node_state_map" href="#dfn-node_state_map">node state map</a>:
+ <ol class="algorithm">
+ <li>If the node's <a class="tref internalDFN" title="label" href="#dfn-label">label</a> does not start with <code>_:</code>
+ then put the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> in the
+ <a class="tref internalDFN" title="list_of_finished_nodes" href="#dfn-list_of_finished_nodes">list of finished nodes</a>.
+ </li>
+ <li>If the node's <a class="tref internalDFN" title="label" href="#dfn-label">label</a> does start with <code>_:</code>
+ then put the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a> in the
+ <a class="tref internalDFN" title="list_of_unfinished_nodes" href="#dfn-list_of_unfinished_nodes">list of unfinished nodes</a>.
+ </li>
+ </ol>
+ </li>
+ <li>Append to the <a class="tref internalDFN" title="list_of_finished_nodes" href="#dfn-list_of_finished_nodes">list of finished nodes</a> by processing
+ the remainder of the <a class="tref internalDFN" title="list_of_unfinished_nodes" href="#dfn-list_of_unfinished_nodes">list of unfinished nodes</a> until it is
+ empty:
+ <ol class="algorithm">
+ <li>Sort the <a class="tref internalDFN" title="list_of_unfinished_nodes" href="#dfn-list_of_unfinished_nodes">list of unfinished nodes</a> in descending order
+ according to the
+ <a href="#deep-comparison-algorithm">Deep Comparison Algorithm</a> to
+ determine the sort order.</li>
+ <li>Create a <dfn title="list_of_labels" id="dfn-list_of_labels">list of labels</dfn> and initialize it to an
+ empty array.</li>
+ <li>For the first node from the <a class="tref internalDFN" title="list_of_unfinished_nodes" href="#dfn-list_of_unfinished_nodes">list of unfinished nodes</a>:
+ <ol class="algorithm">
+ <li>Add its <a class="tref internalDFN" title="label" href="#dfn-label">label</a> to the <a class="tref internalDFN" title="list_of_labels" href="#dfn-list_of_labels">list of labels</a>.
+ </li>
+ <li>For each key-value pair from its associated
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>, add the key to a list and
+ then sort the list according to the lexicographical order of the
+ keys' associated values. Append the list to the
+ <a class="tref internalDFN" title="list_of_nodes_to_label" href="#dfn-list_of_nodes_to_label">list of nodes to label</a>.
+ <span class="issue"><dfn title="list_of_nodes_to_label" id="dfn-list_of_nodes_to_label">list of nodes to label</dfn> not defined.</span>
+ </li>
+ <li>For each key-value pair from its associated
+ <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a>, add the key to a list and
+ then sort the list according to the lexicographical order of the
+ keys' associated values. Append the list to the
+ <a class="tref internalDFN" title="list_of_nodes_to_label" href="#dfn-list_of_nodes_to_label">list of nodes to label</a>.
+ </li></ol></li>
+ <li>For each <a class="tref internalDFN" title="label" href="#dfn-label">label</a> in the <a class="tref internalDFN" title="list_of_labels" href="#dfn-list_of_labels">list of labels</a>,
+ relabel the associated node according to the
+ <a href="#node-relabeling-algorithm">Node Relabeling Algorithm</a>. If
+ any <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a> contains a key that
+ matches the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>, clear the map and set the associated
+ <a class="tref internalDFN" title="outgoing_serialization" href="#dfn-outgoing_serialization">outgoing serialization</a> to an empty string. If any
+ <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a> contains a key that
+ matches the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>, clear the map and set the associated
+ <a class="tref internalDFN" title="incoming_serialization" href="#dfn-incoming_serialization">incoming serialization</a> to an empty string.
+ </li>
+ <li>
+ Remove each node with a <a class="tref internalDFN" title="label" href="#dfn-label">label</a> that starts with
+ <code>_:c14n</code> from the <a class="tref internalDFN" title="list_of_unfinished_nodes" href="#dfn-list_of_unfinished_nodes">list of unfinished nodes</a> and
+ add it to the <a class="tref internalDFN" title="list_of_finished_nodes" href="#dfn-list_of_finished_nodes">list of finished nodes</a>.
+ </li>
+ </ol>
+ </li>
+ <li>Sort the <a class="tref internalDFN" title="list_of_finished_nodes" href="#dfn-list_of_finished_nodes">list of finished nodes</a> in descending order
+ according to the
+ <a href="#deep-comparison-algorithm">Deep Comparison Algorithm</a> to
+ determine the sort order.</li>
+</ol>
+</div>
+
+<div id="shallow-comparison-algorithm" class="section">
+<h4><span class="secno">3.8.6 </span>Shallow Comparison Algorithm</h4>
+
+<p>
+The shallow comparison algorithm takes two unlabeled nodes,
+<a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>, as input and
+determines which one should come first in a sorted list. The following
+algorithm determines the steps that are executed in order to determine the
+node that should come first in a list:
+</p>
+
+<ol class="algorithm">
+ <li>Compare the total number of node properties. The node with fewer
+ properties is first.</li>
+ <li>Lexicographically sort the property <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s for each node and compare
+ the sorted lists. If an IRI is found to be lexicographically smaller, the
+ node containing that IRI is first.</li>
+ <li>Compare the values of each property against one another:
+ <ol class="algorithm">
+ <li>The node associated with fewer property values is first.
+ </li>
+ <li>Create an <dfn title="alpha_list" id="dfn-alpha_list">alpha list</dfn> by adding all values associated
+ with the <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> property that are not unlabeled nodes.
+ </li>
+ <li>Create a <dfn title="beta_list" id="dfn-beta_list">beta list</dfn> by adding all values associated
+ with the <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a> property that is not an unlabeled node.
+ </li>
+ <li>Compare the length of <a class="tref internalDFN" title="alpha_list" href="#dfn-alpha_list">alpha list</a> and
+ <a class="tref internalDFN" title="beta_list" href="#dfn-beta_list">beta list</a>. The node associated with the list containing
+ the fewer number of items is first.</li>
+ <li>Sort <a class="tref internalDFN" title="alpha_list" href="#dfn-alpha_list">alpha list</a> and <a class="tref internalDFN" title="beta_list" href="#dfn-beta_list">beta list</a> according to
+ the
+ <a href="#object-comparison-algorithm">Object Comparison Algorithm</a>.
+ For each offset into the <a class="tref internalDFN" title="alpha_list" href="#dfn-alpha_list">alpha list</a>, compare the item
+ at the offset against the item at the same offset in the
+ <a class="tref internalDFN" title="beta_list" href="#dfn-beta_list">beta list</a> according to the
+ <a href="#object-comparison-algorithm">Object Comparison Algorithm</a>.
+ The node associated with the lesser item is first.
+ </li></ol></li>
+ <li>Process the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a>s associated with each node to
+ determine order:
+ <ol class="algorithm">
+ <li>The node with the shortest <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a> is first.</li>
+ <li>Sort the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a>s according to incoming property
+ and then incoming <a class="tref internalDFN" title="label" href="#dfn-label">label</a>.
+ </li><li>The node associated with the fewest number of incoming nodes is
+ first.</li>
+ <li>For each offset into the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a>s,
+ compare the associated properties and <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s:
+ <ol class="algorithm">
+ <li>The node associated with a <a class="tref internalDFN" title="label" href="#dfn-label">label</a> that does not begin with
+ <code>_:</code> is first.
+ </li>
+ <li>If the nodes' <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s do not begin with
+ <code>_:</code>, then the node associated with the
+ lexicographically lesser <a class="tref internalDFN" title="label" href="#dfn-label">label</a> is first.</li>
+
+ <li>The node associated with the lexicographically lesser associated
+ property is first.
+ </li>
+ <li>The node with the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> that does not begin with
+ <code>_:c14n</code> is first.
+ </li>
+ <li>The node with the lexicographically lesser <a class="tref internalDFN" title="label" href="#dfn-label">label</a>
+ is first.
+ </li>
+ </ol>
+ </li></ol></li>
+ <li>Otherwise, the nodes are equivalent.</li>
+</ol></div>
+
+<div id="object-comparison-algorithm" class="section">
+<h4><span class="secno">3.8.7 </span>Object Comparison Algorithm</h4>
+
+<p>
+The object comparison algorithm is designed to compare two graph node
+property values, <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>, against the other.
+The algorithm is useful when sorting two lists of graph node properties.
+</p>
+
+<ol class="algorithm">
+ <li>If one of the values is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a> and the other is not, the value that is
+ a string is first.
+ </li>
+ <li>If both values are <a class="tref internalDFN" title="string" href="#dfn-string">string</a>s, the lexicographically lesser string is
+ first.
+ </li>
+ <li>If one of the values is a literal and the other is not, the value that is
+ a literal is first.
+ </li>
+ <li>If both values are literals:
+ <ol class="algorithm">
+ <li>The lexicographically lesser string associated with
+ <code>@literal</code> is first.
+ </li>
+ <li>The lexicographically lesser string associated with
+ <code>@datatype</code> is first.
+ </li>
+ <li>The lexicographically lesser string associated with
+ <code>@language</code> is first.
+ </li>
+ </ol>
+ </li>
+ <li>If both values are expanded <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s, the
+ lexicographically lesser string associated with <code>@iri</code>
+ is first.</li>
+ <li>Otherwise, the two values are equivalent.</li>
+</ol>
+
+</div>
+
+<div id="deep-comparison-algorithm" class="section">
+<h4><span class="secno">3.8.8 </span>Deep Comparison Algorithm</h4>
+
+<p>
+The deep comparison algorithm is used to compare the difference between two
+nodes, <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>.
+A deep comparison takes the incoming and outgoing node edges in
+a graph into account if the number of properties and value of those properties
+are identical. The algorithm is helpful when sorting a list of nodes and will
+return whichever node should be placed first in a list if the two nodes are
+not truly equivalent.
+</p>
+
+<p>When performing the steps required by the deep comparison algorithm, it
+is helpful to track state information about mappings. The information
+contained in a <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> is described below.</p>
+
+<dl class="algorithm">
+ <dt><dfn title="mapping_state" id="dfn-mapping_state">mapping state</dfn></dt>
+ <dd>
+ <dl>
+ <dt><dfn title="mapping_counter" id="dfn-mapping_counter">mapping counter</dfn></dt>
+ <dd>
+ Keeps track of the number of nodes that have been mapped to
+ <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s. It is initialized to
+ <code>1</code>.
+ </dd>
+ <dt><dfn title="processed_labels_map" id="dfn-processed_labels_map">processed labels map</dfn></dt>
+ <dd>
+ Keeps track of the <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s of nodes that have already
+ been assigned <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s. It is initialized
+ to an empty map.
+ </dd>
+ <dt><dfn title="serialized_labels_map" id="dfn-serialized_labels_map">serialized labels map</dfn></dt>
+ <dd>
+ Maps a node <a class="tref internalDFN" title="label" href="#dfn-label">label</a> to its associated
+ <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>. It is initialized to an empty map.
+ </dd>
+ <dt><dfn title="adjacent_info_map" id="dfn-adjacent_info_map">adjacent info map</dfn></dt>
+ <dd>
+ Maps a <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> to the node
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a> associated with it, the list of sorted
+ <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s for adjacent nodes, and the map of
+ adjacent node <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s to their associated
+ node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s. It is initialized to an empty map.
+ </dd>
+ <dt><dfn title="key_stack" id="dfn-key_stack">key stack</dfn></dt>
+ <dd>
+ A stack where each element contains an array of adjacent
+ <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s and an index into that array. It
+ is initialized to a stack containing a single element where its
+ array contains a single string element <code>s1</code> and its
+ index is set to <code>0</code>.
+ </dd>
+ <dt><dfn title="serialized_keys" id="dfn-serialized_keys">serialized keys</dfn></dt>
+ <dd>
+ Keeps track of which <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s have already
+ been written at least once to the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a>.
+ It is initialized to an empty map.
+ </dd>
+ <dt><dfn title="serialization_string" id="dfn-serialization_string">serialization string</dfn></dt>
+ <dd>
+ A string that is incrementally updated as a serialization is built.
+ It is initialized to an empty string.
+ </dd>
+ </dl>
+ </dd>
+</dl>
+
+<p>The deep comparison algorithm is as follows:</p>
+
+<ol class="algorithm">
+ <li>Perform a comparison between <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>
+ according to the
+ <a href="#shallow-comparison-algorithm">Shallow Comparison Algorithm</a>.
+ If the result does not show that the two nodes are equivalent, return
+ the result.
+ </li>
+ <li>Compare incoming and outgoing edges for each node, updating their
+ associated <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a> as each node is processed:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a> for <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>
+ is empty, generate the serialization according to the
+ <a href="#node-serialization-algorithm">Node Serialization Algorithm</a>.
+ Provide <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>'s <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a new
+ <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a>,
+ <code>outgoing direction</code> to the algorithm as inputs.
+ </li><li>If the <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a> for <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>
+ is empty, generate the serialization according to the
+ <a href="#node-serialization-algorithm">Node Serialization Algorithm</a>.
+ Provide <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>'s <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a new
+ <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a>, and
+ <code>outgoing direction</code> to the algorithm as inputs.
+ </li><li>If <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>'s <a class="tref internalDFN" title="outgoing_serialization" href="#dfn-outgoing_serialization">outgoing serialization</a> is
+ lexicographically less than <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>'s, then
+ <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> is first. If it is greater, then <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>
+ is first.</li>
+ <li>If the <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a> for <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>
+ is empty, generate the serialization according to the
+ <a href="#node-serialization-algorithm">Node Serialization Algorithm</a>.
+ Provide <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>'s <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a new
+ <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> with its <a class="tref internalDFN" title="serialized_labels_map" href="#dfn-serialized_labels_map">serialized labels map</a>
+ set to a copy of <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>'s
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>, and
+ <code>incoming direction</code> to the algorithm as inputs.
+ </li><li>If the <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a> for <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>
+ is empty, generate the serialization according to the
+ <a href="#node-serialization-algorithm">Node Serialization Algorithm</a>.
+ Provide <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>'s <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a new
+ <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> with its <a class="tref internalDFN" title="serialized_labels_map" href="#dfn-serialized_labels_map">serialized labels map</a>
+ set to a copy of <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>'s
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>, and
+ <code>incoming direction</code> to the algorithm as inputs.
+ </li><li>If <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>'s <a class="tref internalDFN" title="incoming_serialization" href="#dfn-incoming_serialization">incoming serialization</a> is
+ lexicographically less than <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>'s, then
+ <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> is first. If it is greater, then <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a>
+ is first.</li>
+ </ol></li>
+</ol>
+</div>
+
+<div id="node-serialization-algorithm" class="section">
+<h4><span class="secno">3.8.9 </span>Node Serialization Algorithm</h4>
+
+<p>
+The node serialization algorithm takes a <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a
+<a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a>, and a <dfn title="direction" id="dfn-direction">direction</dfn> (either
+<code>outgoing direction</code> or <code>incoming direction</code>) as
+inputs and generates a deterministic serialization for the
+<a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>.
+</p>
+
+<ol class="algorithm">
+<li>If the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> exists in the
+ <a class="tref internalDFN" title="processed_labels_map" href="#dfn-processed_labels_map">processed labels map</a>, terminate the algorithm as the
+ <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> has already been created.
+</li>
+<li>Set the value associated with the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> in the
+ <a class="tref internalDFN" title="processed_labels_map" href="#dfn-processed_labels_map">processed labels map</a> to <code>true</code>.
+</li>
+<li>Generate the next <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> for the
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a> according to the
+ <a href="#serialization-label-generation-algorithm">Serialization Label Generation Algorithm</a>.
+</li>
+<li>Create an empty map called the <dfn title="adjacent_serialized_labels_map" id="dfn-adjacent_serialized_labels_map">adjacent serialized labels map</dfn>
+that will store mappings from <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s to adjacent
+node <a class="tref internalDFN" title="label" href="#dfn-label">label</a>s.</li>
+<li>Create an empty array called the
+<dfn title="adjacent_unserialized_labels_list" id="dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</dfn> that will store
+<a class="tref internalDFN" title="label" href="#dfn-label">label</a>s of adjacent nodes that haven't been assigned
+<a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>s yet.
+</li>
+<li>For every <a class="tref internalDFN" title="label" href="#dfn-label">label</a> in a list, where the list the <a class="tref internalDFN" title="outgoing_list" href="#dfn-outgoing_list">outgoing list</a> if
+the <a class="tref internalDFN" title="direction" href="#dfn-direction">direction</a> is <code>outgoing direction</code> and the
+<a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a> otherwise, if the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> starts with
+<code>_:</code>, it is the <dfn title="target_node_label" id="dfn-target_node_label">target node label</dfn>:
+ <ol class="algorithm">
+ <li>Look up the <a class="tref internalDFN" title="target_node_label" href="#dfn-target_node_label">target node label</a> in the
+ <a class="tref internalDFN" title="processed_labels_map" href="#dfn-processed_labels_map">processed labels map</a> and if a mapping exists,
+ update the <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a> where the key is
+ the value in the <a class="tref internalDFN" title="serialization_map" href="#dfn-serialization_map">serialization map</a>
+ (<span class="issue"><dfn title="serialization_map" id="dfn-serialization_map">serialization map</dfn> is used, but should it be <a class="tref internalDFN" title="directed_serialization_map" href="#dfn-directed_serialization_map">directed serialization map</a>,
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>or <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a>?</span>)
+ and the value is the
+ <a class="tref internalDFN" title="target_node_label" href="#dfn-target_node_label">target node label</a>.</li>
+ <li>Otherwise, add the <a class="tref internalDFN" title="target_node_label" href="#dfn-target_node_label">target node label</a> to the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a>.
+ </li></ol>
+</li>
+<li>Set the <dfn title="maximum_serialization_combinations" id="dfn-maximum_serialization_combinations">maximum serialization combinations</dfn> to
+ <code>1</code> or the length of the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a>, whichever is greater.</li>
+<li>While the <a class="tref internalDFN" title="maximum_serialization_combinations" href="#dfn-maximum_serialization_combinations">maximum serialization combinations</a> is greater than
+ <code>0</code>, perform the
+ <a href="#combinatorial-serialization-algorithm">Combinatorial Serialization Algorithm</a>
+ passing the <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, the <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> for the
+ first iteration and a copy of it for each subsequent iteration, the
+ generated <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>, the <a class="tref internalDFN" title="direction" href="#dfn-direction">direction</a>,
+ the <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a>, and the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a>.
+ Decrement the <a class="tref internalDFN" title="maximum_serialization_combinations" href="#dfn-maximum_serialization_combinations">maximum serialization combinations</a> by
+ <code>1</code> for each iteration.
+</li></ol>
+
+</div>
+
+<div id="serialization-label-generation-algorithm" class="section">
+<h4><span class="secno">3.8.10 </span>Serialization Label Generation Algorithm</h4>
+
+<p>
+The algorithm generates a <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> given a
+<a class="tref internalDFN" title="label" href="#dfn-label">label</a> and a <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> and returns the
+<a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>.
+</p>
+
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> is already in the
+ <a class="tref internalDFN" title="serialization_labels_map" href="#dfn-serialization_labels_map">serialization labels map</a>, return its associated value.
+ (<span class="issue"><dfn title="serialization_labels_map" id="dfn-serialization_labels_map">serialization labels map</dfn> is used, but should it be <a class="tref internalDFN" title="directed_serialization_map" href="#dfn-directed_serialization_map">directed serialization map</a>,
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>or <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a>?</span>)
+ </li>
+ <li>If the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> starts with the string <code>_:c14n</code>,
+ the <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> is the letter <code>c</code>
+ followed by the number that follows <code>_:c14n</code> in the
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a>.
+ </li>
+ <li>Otherwise, the <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> is the
+ letter <code>s</code> followed by the string value of
+ <a class="tref internalDFN" title="mapping_counter" href="#dfn-mapping_counter">mapping counter</a>. Increment the <a class="tref internalDFN" title="mapping_counter" href="#dfn-mapping_counter">mapping counter</a> by
+ <code>1</code>.
+ </li>
+ <li>Create a new key-value pair in the <a class="tref internalDFN" title="serialization_labels_map" href="#dfn-serialization_labels_map">serialization labels map</a>
+ where the key is the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> and the value is the
+ generated <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>.
+ </li>
+ </ol>
+</div>
+
+<div id="combinatorial-serialization-algorithm" class="section">
+<h4><span class="secno">3.8.11 </span>Combinatorial Serialization Algorithm</h4>
+
+<p>
+The combinatorial serialization algorithm takes a <a class="tref internalDFN" title="node_state" href="#dfn-node_state">node state</a>, a
+<a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a>, a <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>, a
+<a class="tref internalDFN" title="direction" href="#dfn-direction">direction</a>, a <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a>,
+and a <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a> as inputs and generates
+the lexicographically least serialization of nodes relating to the
+<a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>.
+</p>
+
+<ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a> is not empty:
+ <ol class="algorithm">
+ <li>Copy the <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a> to the
+ <dfn title="adjacent_serialized_labels_map_copy" id="dfn-adjacent_serialized_labels_map_copy">adjacent serialized labels map copy</dfn>.</li>
+ <li>Remove the first <dfn title="unserialized_label" id="dfn-unserialized_label">unserialized label</dfn> from the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a> and create a new
+ <dfn title="new_serialization_label" id="dfn-new_serialization_label">new serialization label</dfn> according to the
+ <a href="#serialization-label-generation-algorithm">Serialization Label Generation Algorithm</a>.
+ </li><li>Create a new key-value mapping in the
+ <a class="tref internalDFN" title="adjacent_serialized_labels_map_copy" href="#dfn-adjacent_serialized_labels_map_copy">adjacent serialized labels map copy</a>
+ where the key is the <a class="tref internalDFN" title="new_serialization_label" href="#dfn-new_serialization_label">new serialization label</a> and the value
+ is the <a class="tref internalDFN" title="unserialized_label" href="#dfn-unserialized_label">unserialized label</a>.
+ </li><li>Set the <dfn title="maximum_serialization_rotations" id="dfn-maximum_serialization_rotations">maximum serialization rotations</dfn> to
+ <code>1</code> or the length of the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a>, whichever is greater.
+ </li>
+ <li>While the <a class="tref internalDFN" title="maximum_serialization_rotations" href="#dfn-maximum_serialization_rotations">maximum serialization rotations</a> is greater than
+ <code>0</code>:
+ <ol class="algorithm">
+ <li>Recursively perform the
+ <a href="#combinatorial-serialization-algorithm">Combinatorial Serialization Algorithm</a>
+ passing the <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a> for the first iteration of the
+ loop, and a copy of it for each subsequent iteration.
+ </li>
+ <li>Rotate the elements in the
+ <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a> by shifting each of
+ them once to the right, moving the element at the end of the list
+ to the beginning of the list.
+ </li>
+ <li>Decrement the <a class="tref internalDFN" title="maximum_serialization_rotations" href="#dfn-maximum_serialization_rotations">maximum serialization rotations</a> by
+ <code>1</code> for each iteration.
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If the <a class="tref internalDFN" title="adjacent_unserialized_labels_list" href="#dfn-adjacent_unserialized_labels_list">adjacent unserialized labels list</a> is empty:
+ <ol class="algorithm">
+ <li>Create a <dfn title="list_of_keys" id="dfn-list_of_keys">list of keys</dfn> from the keys in the
+ <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a> and sort it
+ lexicographically.
+ </li>
+ <li>Add a key-value pair to the <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a> where
+ the key is the <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a> and the value is
+ an object containing the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>'s label, the
+ <a class="tref internalDFN" title="list_of_keys" href="#dfn-list_of_keys">list of keys</a> and the
+ <a class="tref internalDFN" title="adjacent_serialized_labels_map" href="#dfn-adjacent_serialized_labels_map">adjacent serialized labels map</a>.
+ </li>
+ <li>Update the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> according to the
+ <a href="#mapping-serialization-algorithm">Mapping Serialization Algorithm</a>.
+ </li>
+ <li>If the <a class="tref internalDFN" title="direction" href="#dfn-direction">direction</a> is <code>outgoing direction</code>
+ then <dfn title="directed_serialization" id="dfn-directed_serialization">directed serialization</dfn> refers to the
+ <a class="tref internalDFN" title="outgoing_serialization" href="#dfn-outgoing_serialization">outgoing serialization</a> and the
+ <dfn title="directed_serialization_map" id="dfn-directed_serialization_map">directed serialization map</dfn> refers to the
+ <a class="tref internalDFN" title="outgoing_serialization_map" href="#dfn-outgoing_serialization_map">outgoing serialization map</a>, otherwise it refers to the
+ <a class="tref internalDFN" title="incoming_serialization" href="#dfn-incoming_serialization">incoming serialization</a> and the
+ <a class="tref internalDFN" title="directed_serialization_map" href="#dfn-directed_serialization_map">directed serialization map</a> refers to the
+ <a class="tref internalDFN" title="incoming_serialization_map" href="#dfn-incoming_serialization_map">incoming serialization map</a>. Compare the
+ <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> to the
+ <a class="tref internalDFN" title="directed_serialization" href="#dfn-directed_serialization">directed serialization</a> according to the
+ <a href="#mapping-serialization-algorithm">Serialization Comparison Algorithm</a>.
+ If the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> is less than or equal to
+ the <a class="tref internalDFN" title="directed_serialization" href="#dfn-directed_serialization">directed serialization</a>:
+ <ol class="algorithm">
+ <li>For each value in the <a class="tref internalDFN" title="list_of_keys" href="#dfn-list_of_keys">list of keys</a>, run the
+ <a href="#node-serialization-algorithm">Node Serialization Algorithm</a>.
+ </li>
+ <li>Update the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> according to the
+ <a href="#mapping-serialization-algorithm">Mapping Serialization Algorithm</a>.
+ </li>
+ <li>Compare the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> to the
+ <a class="tref internalDFN" title="directed_serialization" href="#dfn-directed_serialization">directed serialization</a> again and if it is less than
+ or equal and the length of the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> is
+ greater than or equal to the length of the
+ <a class="tref internalDFN" title="directed_serialization" href="#dfn-directed_serialization">directed serialization</a>, then set the
+ <a class="tref internalDFN" title="directed_serialization" href="#dfn-directed_serialization">directed serialization</a> to the
+ <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> and set the
+ <a class="tref internalDFN" title="directed_serialization_map" href="#dfn-directed_serialization_map">directed serialization map</a> to the
+ <a class="tref internalDFN" title="serialized_labels_map" href="#dfn-serialized_labels_map">serialized labels map</a>.
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+</ol>
+
+</div>
+
+<div id="serialization-comparison-algorithm" class="section">
+<h4><span class="secno">3.8.12 </span>Serialization Comparison Algorithm</h4>
+
+<p>
+The serialization comparison algorithm takes two serializations,
+<a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a> and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a> and returns either which of the two
+is less than the other or that they are equal.
+</p>
+
+<ol class="algorithm">
+ <li>Whichever serialization is an empty string is greater. If they are
+ both empty strings, they are equal.</li>
+ <li>Return the result of a lexicographical comparison of <a class="tref internalDFN" title="alpha" href="#dfn-alpha">alpha</a>
+ and <a class="tref internalDFN" title="beta" href="#dfn-beta">beta</a> up to the number of characters in the shortest of
+ the two serializations.
+ </li>
+</ol>
+</div>
+
+<div id="mapping-serialization-algorithm" class="section">
+<h4><span class="secno">3.8.13 </span>Mapping Serialization Algorithm</h4>
+
+<p>
+The mapping serialization algorithm incrementally updates the
+<a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a> in a <a class="tref internalDFN" title="mapping_state" href="#dfn-mapping_state">mapping state</a>.
+</p>
+
+<ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="key_stack" href="#dfn-key_stack">key stack</a> is not empty:
+ <ol class="algorithm">
+ <li>Pop the <dfn title="serialization_key_info" id="dfn-serialization_key_info">serialization key info</dfn> off of the
+ <a class="tref internalDFN" title="key_stack" href="#dfn-key_stack">key stack</a>.
+ </li>
+ <li>For each <dfn title="serialization_key" id="dfn-serialization_key">serialization key</dfn> in the
+ <a class="tref internalDFN" title="serialization_key_info" href="#dfn-serialization_key_info">serialization key info</a> array, starting at
+ the <dfn title="serialization_key_index" id="dfn-serialization_key_index">serialization key index</dfn> from the
+ <a class="tref internalDFN" title="serialization_key_info" href="#dfn-serialization_key_info">serialization key info</a>:
+ <ol class="algorithm">
+ <li>If the <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> is not in the
+ <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a>, push the
+ <a class="tref internalDFN" title="serialization_key_info" href="#dfn-serialization_key_info">serialization key info</a> onto the
+ <a class="tref internalDFN" title="key_stack" href="#dfn-key_stack">key stack</a> and exit from this loop.
+ </li>
+ <li>If the <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> is a key in
+ <a class="tref internalDFN" title="serialized_keys" href="#dfn-serialized_keys">serialized keys</a>, a cycle has been detected. Append
+ the concatenation of the <code>_</code> character and the
+ <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> to the
+ <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a>.
+ </li><li>Otherwise, serialize all outgoing and incoming edges in the
+ related node by performing the following steps:
+ <ol class="algorithm">
+ <li>Mark the <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> as having
+ been processed by adding a new key-value pair to
+ <a class="tref internalDFN" title="serialized_keys" href="#dfn-serialized_keys">serialized keys</a> where the key
+ is the <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> and the value is
+ <code>true</code>.
+ </li>
+ <li>Set the <dfn title="serialization_fragment" id="dfn-serialization_fragment">serialization fragment</dfn> to the value of
+ the <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a>.</li>
+ <li>Set the <dfn title="adjacent_info" id="dfn-adjacent_info">adjacent info</dfn> to the value of the
+ <a class="tref internalDFN" title="serialization_key" href="#dfn-serialization_key">serialization key</a> in the
+ <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a>.
+ </li>
+ <li>Set the <dfn title="adjacent_node_label" id="dfn-adjacent_node_label">adjacent node label</dfn> to the node
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a> from the <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a>.
+ </li>
+ <li>If a mapping for the <a class="tref internalDFN" title="adjacent_node_label" href="#dfn-adjacent_node_label">adjacent node label</a>
+ exists in the <a class="tref internalDFN" title="map_of_all_labels" href="#dfn-map_of_all_labels">map of all labels</a>:
+ <ol class="algorithm">
+ <li>Append the result of the
+ <a href="">Label Serialization Algorithm</a> to the
+ <a class="tref internalDFN" title="serialization_fragment" href="#dfn-serialization_fragment">serialization fragment</a>.
+ </li>
+ </ol>
+ <span class="issue"><dfn title="map_of_all_labels" id="dfn-map_of_all_labels">map of all labels</dfn> referenced but not defined.</span>
+ </li>
+ <li>Append all of the keys in the <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a>
+ to the <a class="tref internalDFN" title="serialization_fragment" href="#dfn-serialization_fragment">serialization fragment</a>.
+ </li>
+ <li>Append the <a class="tref internalDFN" title="serialization_fragment" href="#dfn-serialization_fragment">serialization fragment</a> to the
+ <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a>.
+ </li>
+ <li>Push a new key info object containing the keys from the
+ <a class="tref internalDFN" title="adjacent_info_map" href="#dfn-adjacent_info_map">adjacent info map</a> and an index of <code>0</code>
+ onto the <a class="tref internalDFN" title="key_stack" href="#dfn-key_stack">key stack</a>.
+ </li>
+ <li>Recursively update the <a class="tref internalDFN" title="serialization_string" href="#dfn-serialization_string">serialization string</a>
+ according to the
+ <a href="#mapping-serialization-algorithm">Mapping Serialization Algorithm</a>.
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+</ol>
+
+</div>
+
+<div id="label-serialization-algorithm" class="section">
+<h4><span class="secno">3.8.14 </span>Label Serialization Algorithm</h4>
+
+<p>
+The label serialization algorithm serializes information about a node that
+has been assigned a particular <a class="tref internalDFN" title="serialization_label" href="#dfn-serialization_label">serialization label</a>.
+</p>
+
+<ol class="algorithm">
+ <li>Initialize the <dfn title="label_serialization" id="dfn-label_serialization">label serialization</dfn> to an empty string.</li>
+ <li>Append the <code>[</code> character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append all properties to the <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a> by
+ processing each key-value pair in the <a class="tref internalDFN" title="node_reference" href="#dfn-node_reference">node reference</a>,
+ excluding the
+ <code>@subject</code> property. The keys should be processed in
+ lexicographical order and their associated values should be processed
+ in the order produced by the
+ <a href="#object-comparison-algorithm">Object Comparison Algorithm</a>:
+ <ol class="algorithm">
+ <li>Build a string using the pattern <code><</code><strong>KEY</strong><code>></code>
+ where <strong>KEY</strong> is the current key. Append string to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>The value may be a single object or an array of objects.
+ Process all of the objects that are associated with the key, building
+ an <dfn title="object_string" id="dfn-object_string">object string</dfn> for each item:
+ <ol class="algorithm">
+ <li>If the object contains an <code>@iri</code> key with a
+ value that starts
+ with <code>_:</code>, set the <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a> to
+ the value <code>_:</code>. If the value does not
+ start with <code>_:</code>, build the <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a>
+ using the pattern
+ <code><</code><strong>IRI</strong><code>></code>
+ where <strong>IRI</strong> is the value associated with the
+ <code>@iri</code> key.</li>
+ <li>If the object contains a <code>@literal</code> key and a
+ <code>@datatype</code> key, build the <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a>
+ using the pattern
+ <code>"</code><strong>LITERAL</strong><code>"^^<</code><strong>DATATYPE</strong><code>></code>
+ where <strong>LITERAL</strong> is the value associated with the
+ <code>@literal</code> key and <strong>DATATYPE</strong> is the
+ value associated with the <code>@datatype</code> key.</li>
+ <li>If the object contains a <code>@literal</code> key and a
+ <code>@language</code> key, build the <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a>
+ using the pattern
+ <code>"</code><strong>LITERAL</strong><code>"@</code><strong>LANGUAGE</strong>
+ where <strong>LITERAL</strong> is the value associated with the
+ <code>@literal</code> key and <strong>LANGUAGE</strong> is the
+ value associated with the <code>@language</code> key.</li>
+ <li>Otherwise, the value is a string. Build the
+ <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a> using the pattern
+ <code>"</code><strong>LITERAL</strong><code>"</code>
+ where <strong>LITERAL</strong> is the value associated with the
+ current key.</li>
+ <li>If this is the second iteration of the loop,
+ append a <code>|</code> separator character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append the <a class="tref internalDFN" title="object_string" href="#dfn-object_string">object string</a> to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ </ol>
+ </li></ol>
+ </li>
+ <li>Append the <code>]</code> character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append the <code>[</code> character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append all incoming references for the current
+ <a class="tref internalDFN" title="label" href="#dfn-label">label</a> to the <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a> by
+ processing all of the items associated with the <a class="tref internalDFN" title="incoming_list" href="#dfn-incoming_list">incoming list</a>:
+ <ol class="algorithm">
+ <li>Build a <dfn title="reference_string" id="dfn-reference_string">reference string</dfn>
+ using the pattern <code><</code><strong>PROPERTY</strong><code>></code><code><</code><strong>REFERER</strong><code>></code>
+ where <strong>PROPERTY</strong> is the property associated with the
+ incoming reference and <strong>REFERER</strong> is either the subject of
+ the node referring to the <a class="tref internalDFN" title="label" href="#dfn-label">label</a> in the incoming reference
+ or <code>_:</code> if <strong>REFERER</strong> begins with
+ <code>_:</code>.
+ </li><li>If this is the second iteration of the loop,
+ append a <code>|</code> separator character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append the <a class="tref internalDFN" title="reference_string" href="#dfn-reference_string">reference string</a> to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ </ol>
+ </li><li>Append the <code>]</code> character to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.</li>
+ <li>Append all <a class="tref internalDFN" title="adjacent_node_labels" href="#dfn-adjacent_node_labels">adjacent node labels</a> to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a> by concatenating the string value
+ for all of them, one after the other, to the
+ <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.
+ <span class="issue"><dfn title="adjacent_node_labels" id="dfn-adjacent_node_labels">adjacent node labels</dfn> referenced but not defined.</span></li>
+ <li>Push the <a class="tref internalDFN" title="adjacent_node_labels" href="#dfn-adjacent_node_labels">adjacent node labels</a> onto the
+ <a class="tref internalDFN" title="key_stack" href="#dfn-key_stack">key stack</a> and append the result of the
+ <a href="#mapping-serialization-algorithm">Mapping Serialization Algorithm</a>
+ to the <a class="tref internalDFN" title="label_serialization" href="#dfn-label_serialization">label serialization</a>.
+</li></ol>
+
+</div>
+
+</div>
+
+<div id="data-round-tripping" class="section">
+
+<h3><span class="secno">3.9 </span>Data Round Tripping</h3>
+
+<p>When normalizing <strong>xsd:double</strong> values, implementers <em class="rfc2119" title="must">must</em>
+ensure that the normalized value is a string. In order to generate the
+string from a <strong>double</strong> value, output equivalent to the
+<code>printf("%1.6e", value)</code> function in C <em class="rfc2119" title="must">must</em> be used where
+<strong>"%1.6e"</strong> is the string formatter and <strong>value</strong>
+is the value to be converted.</p>
+
+<p>To convert the a double value in JavaScript, implementers can use the
+following snippet of code:</p>
+
+<pre class="example">// the variable 'value' below is the JavaScript native double value that is to be converted
+(value).toExponential(6).replace(/(e(?:\+|-))([0-9])$/, '$10$2')</pre>
+
+<p class="note">When data needs to be normalized, JSON-LD authors should
+not use values that are going to undergo automatic conversion. This is due
+to the lossy nature of <strong>xsd:double</strong> values.</p>
+
+<p class="note">Some JSON serializers, such as PHP's native implementation,
+backslash-escapes the forward slash character. For example, the value
+<code>http://example.com/</code> would be serialized as
+<code>http:\/\/example.com\/</code> in some
+versions of PHP. This is problematic when generating a byte
+stream for processes such as normalization. There is no need to
+backslash-escape forward-slashes in JSON-LD. To aid interoperability between
+JSON-LD processors, a JSON-LD serializer <em class="rfc2119" title="must not">must not</em> backslash-escape
+forward slashes.</p>
+
+<p class="issue">Round-tripping data can be problematic if we mix and
+match @coerce rules with JSON-native datatypes, like integers. Consider the
+following code example:</p>
+
+<pre class="example">var myObj = { "@context" : {
+ "number" : "http://example.com/vocab#number",
+ "@coerce": {
+ "xsd:nonNegativeInteger": "number"
+ }
+ },
+ "number" : 42 };
+
+// Map the language-native object to JSON-LD
+var jsonldText = jsonld.normalize(myObj);
+
+// Convert the normalized object back to a JavaScript object
+var myObj2 = jsonld.parse(jsonldText);</pre>
+
+<p class="issue">At this point, myObj2 and myObj will have different
+values for the "number" value. myObj will be the number 42, while
+myObj2 will be the string "42". This type of data round-tripping
+error can bite developers. We are currently wondering if having a
+"coerce validation" phase in the parsing/normalization phases would be a
+good idea. It would prevent data round-tripping issues like the
+one mentioned above.</p>
+
+</div>
+
+<div id="rdf-conversion" class="section">
+<h3><span class="secno">3.10 </span>RDF Conversion</h3>
+
+<p>A JSON-LD document <em class="rfc2119" title="may">may</em> be converted to any other RDF-compatible document
+format using the algorithm specified in this section.</p>
+
+<p>
+ The JSON-LD Processing Model describes processing rules for extracting RDF
+ from a JSON-LD document. Note that many uses of JSON-LD may not require
+ generation of RDF.
+</p>
+
+<p>
+The processing algorithm described in this section is provided in
+order to demonstrate how one might implement a JSON-LD to RDF processor.
+Conformant implementations are only required to produce the same type and
+number of triples during the output process and are not required to
+implement the algorithm exactly as described.
+</p>
+
+<p class="issue">The RDF Conversion Algorithm is a work in progress.</p>
+
+<div class="informative section" id="overview">
+ <h4><span class="secno">3.10.1 </span>Overview</h4><p><em>This section is non-normative.</em></p>
+ <p>
+ JSON-LD is intended to have an easy to parse grammar that closely models existing
+ practice in using JSON for describing object representations. This allows the use
+ of existing libraries for parsing JSON.
+ </p>
+ <p>
+ As with other grammars used for describing <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, a key concept is that of
+ a <em>resource</em>. Resources may be of three basic types: <em><a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a></em>s, for describing
+ externally named entities, <em>BNodes</em>, resources for which an external name does not
+ exist, or is not known, and Literals, which describe terminal entities such as strings,
+ dates and other representations having a lexical representation possibly including
+ an explicit language or datatype.
+ </p>
+ <p>
+ An Internationalized Resource Identifier
+ (<dfn title="iri" id="dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></dfn>),
+ as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>], is a mechanism for representing unique
+ identifiers on the web. In <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, an IRI is commonly
+ used for expressing a <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>, a <a class="tref internalDFN" title="property" href="#dfn-property">property</a> or an
+ <a class="tref internalDFN" title="object" href="#dfn-object">object</a>.
+ </p>
+ <p>
+ Data described with JSON-LD may be considered to be the representation of a graph made
+ up of <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> and <a class="tref internalDFN" title="object" href="#dfn-object">object</a> resources related via a <a class="tref internalDFN" title="property" href="#dfn-property">property</a> resource.
+ However, specific implementations may choose to operate on the document as a normal
+ JSON description of objects having attributes.
+ </p>
+</div>
+
+<div id="rdf-conversion-algorithm-terms" class="section">
+ <h4><span class="secno">3.10.2 </span>RDF Conversion Algorithm Terms</h4>
+ <dl>
+ <dt><dfn title="default_graph" id="dfn-default_graph">default graph</dfn></dt>
+ <dd>
+ the destination graph for all triples generated by JSON-LD markup.
+ </dd>
+ </dl>
+</div>
+
+<div id="rdf-conversion-algorithm" class="section">
+ <h4><span class="secno">3.10.3 </span>RDF Conversion Algorithm</h4>
+ <p>
+ The algorithm below is designed for in-memory implementations with random access to <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> elements.
+ </p>
+ <p>
+ A conforming JSON-LD processor implementing RDF conversion <em class="rfc2119" title="must">must</em> implement a
+ processing algorithm that results in the same <a class="tref internalDFN" title="default_graph" href="#dfn-default_graph">default graph</a> that the following
+ algorithm generates:
+ </p>
+
+ <ol class="algorithm">
+ <li id="processing-step-default-context">
+ Create a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> with with the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> set to the
+ <a class="tref internalDFN" title="initial_context" href="#dfn-initial_context">initial context</a> and <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> and <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>
+ initialized to NULL.
+ </li>
+
+ <li id="processing-step-associative">
+ If a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is detected, perform the following steps:
+ <ol class="algorithm">
+ <li>
+ If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> has a <code>@context</code> key, process the local context as
+ described in <a href="#context">Context</a>.
+ </li>
+ <li>
+ Create a new <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> by mapping the keys from the current <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> using the
+ <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> to new keys using the associated value from the current <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>.
+ Repeat the mapping until no entry is found within the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> for the key. Use the new
+ <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> in subsequent steps.
+ </li>
+ <li>
+ If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> has an <code>@iri</code> key, set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> by
+ performing <a href="#iri-expansion">IRI Expansion</a> on the associated value. Generate a
+ triple representing the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the
+ <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>. Return the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> to the calling location.
+ <p class="issue"><code>@iri</code> really just behaves the same as <code>@subject</code>, consider consolidating them.</p>
+ </li>
+ <li>
+ If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> has a <code>@literal</code> key, set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>
+ to a literal value as follows:
+ <ol class="algorithm">
+ <li>
+ as a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> if the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> contains a <code>@datatype</code> key
+ after performing <a href="#iri-expansion">IRI Expansion</a> on the specified<code>@datatype</code>.
+ </li>
+ <li>
+ otherwise, as a <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>. If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> contains
+ a <code>@language</code> key, use it's value to set the language of the plain literal.
+ </li>
+ <li>
+ Generate a triple representing the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the
+ <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>. Return the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> to the calling location.
+ </li>
+ </ol>
+ </li>
+ <li>
+ If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> has a <code>@list</code> key and the value is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>
+ process the value as a list starting at <a href="#processing-step-list">Step 4</a>.
+ </li>
+ <li id="processing-step-subject">If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> has a <code>@subject</code> key:
+ <ol class="algorithm">
+ <li>
+ If the value is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> to the result of performing
+ <a href="#iri-expansion">IRI Expansion</a>. Generate a
+ triple representing the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the
+ <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>. Set the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> to the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>.
+ </li>
+ <li>
+ Create a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> copies of the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>,
+ <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> and <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>.
+ <ol class="algorithm">
+ <li>
+ If the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> is the target of a <code>@list</code> coercion,
+ and the value is an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>,
+ process the value as a list starting at <a href="#processing-step-list">Step 4</a>.
+ </li>
+ <li>
+ Otherwise, process the value starting at
+ <a href="#processing-step-associative">Step 2</a>.
+ </li>
+ <li>Proceed using the previous <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>
+ If the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> does not have a <code>@subject</code> key, set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active
+ object</a> to newly generated <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>. Generate a triple
+ representing the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the
+ <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>. Set the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> to the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active
+ object</a>.
+ </li>
+ <li>
+ For each key in the <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that has not already been processed, perform
+ the following steps:
+ <ol class="algorithm">
+ <li>
+ If the key is <code>@type</code>, set the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>
+ to <code>rdf:type</code>.
+ </li>
+ <li>Otherwise, set the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> to the result of performing
+ <a href="#iri-expansion">IRI Expansion</a> on the key.</li>
+ <li>
+ Create a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> copies of the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>,
+ <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> and <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and process the value
+ starting at <a href="#processing-step-associative">Step 2</a> and proceed using the
+ previous <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>.
+ </li>
+ </ol>
+ </li>
+ <li>
+ Return the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> to the calling location.
+ </li>
+ </ol>
+ </li>
+
+ <li>
+ If a regular <a class="tref internalDFN" title="array" href="#dfn-array">array</a> is detected, process each value in the <a class="tref internalDFN" title="array" href="#dfn-array">array</a> by doing the following
+ returning the result of processing the last value in the <a class="tref internalDFN" title="array" href="#dfn-array">array</a>:
+
+ <ol class="algorithm">
+ <li>
+ Create a new <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a> using copies of the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active
+ context</a>, <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a> and <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and process the value
+ starting at <a href="#processing-step-associative">Step 2</a> then proceed using the previous
+ <a class="tref internalDFN" title="processor_state" href="#dfn-processor_state">processor state</a>.
+ </li>
+ </ol>
+ </li>
+
+ <li id="processing-step-list">
+ Generate an RDF List by linking
+ each element of the list using <code>rdf:first</code> and <code>rdf:next</code>, terminating the list with <code>rdf:nil</code>
+ using the following sequence:
+ <ol class="algorithm">
+ <li>
+ If the list has no element, generate a triple using the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>
+ and <code>rdf:nil</code>.
+ </li>
+ <li>
+ Otherwise, generate a triple using using the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>
+ and a newly generated BNode identified as <em>first <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em>.
+ </li>
+ <li>
+ For each element other than the last element in the list:
+ <ol class="algorithm">
+ <li>Create a processor state using the active context, <em>first <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em> as the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, and <code>rdf:first</code> as the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>.</li>
+ <li>Unless this is the last element in the list, generate a new BNode identified as <em>rest <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em>, otherwise use <code>rdf:nil</code>.</li>
+ <li>Generate a new triple using <em>first <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em>, <code>rdf:rest</code> and <em>rest <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em>.</li>
+ <li>Set <em>first <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em> to <em>rest <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a></em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+
+ <li>
+ If a <a class="tref internalDFN" title="string" href="#dfn-string">string</a> is detected:
+ <ol class="algorithm">
+ <li>
+ If the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> is the target of a <code>@iri</code> coercion,
+ set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> by
+ performing <a href="#iri-expansion">IRI Expansion</a> on the string.
+ </li>
+ <li>
+ Otherwise, if the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> is the target of coercion,
+ set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> by creating a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> using
+ the string and the coercion key as the datatype IRI.
+ </li>
+ <li>
+ Otherwise, set the <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a> to a <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a> value created from the string.
+ If the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> contains a <code>language</code> key with a non-<code>null</code> value,
+ use it's value to set the language of the <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>.
+ </li>
+ </ol>
+ Generate a
+ triple representing the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, the <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the
+ <a class="tref internalDFN" title="active_object" href="#dfn-active_object">active object</a>.
+ </li>
+
+ <li>
+ If a <a class="tref internalDFN" title="number" href="#dfn-number">number</a> is detected, generate a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> using a string representation of
+ the value with datatype set to either <code>xsd:integer</code> or
+ <code>xsd:double</code>, depending on if the value contains a
+ fractional and/or an exponential component. Generate a triple using the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active
+ subject</a>, <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a> and the generated typed literal.
+ </li>
+
+ <li>
+ Otherwise, if <strong>true</strong> or <strong>false</strong> is detected,
+ generate a triple using the <a class="tref internalDFN" title="active_subject" href="#dfn-active_subject">active subject</a>, <a class="tref internalDFN" title="active_property" href="#dfn-active_property">active property</a>
+ and a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> value created from the string representation of the
+ value with datatype set to <code>xsd:boolean</code>.
+ </li>
+ </ol>
+</div>
+
+<div class="appendix section" id="acknowledgements">
+<h4><span class="secno">3.10.4 </span>Acknowledgements</h4>
+
+<p>The editors would like to thank Mark Birbeck, who provided a great deal of
+the initial push behind the JSON-LD work via his work on RDFj,
+Dave Longley, Dave Lehn and Mike Johnson who reviewed, provided feedback, and
+performed several implementations of the specification, and Ian Davis, who
+created RDF/JSON. Thanks also to Nathan Rixham, Bradley P. Allen,
+Kingsley Idehen, Glenn McDonald, Alexandre Passant, Danny Ayers, Ted
+Thibodeau Jr., Olivier Grisel, Niklas Lindström, Markus Lanthaler, and Richard
+Cyganiak for their input on the specification. Another huge thank you goes out
+to Dave Longley who designed many of the algorithms used in this specification,
+including the normalization algorithm which was a monumentally difficult
+design challenge.
+</p>
+</div>
+
+
+
+</div></div><div id="respec-err" style="position: fixed; width: 350px; top: 10px; right: 10px; border: 3px double #f00; background: #fff" class="removeOnSave"><ul><li style="color: #c00">There appears to have been a problem fetching the style sheet; status=0</li></ul></div><div id="references" class="appendix section">
+<!-- OddPage -->
+<h2><span class="secno">A. </span>References</h2><div id="normative-references" class="section"><h3><span class="secno">A.1 </span>Normative references</h3><dl class="bibliography"><dt id="bib-JSON-LD">[JSON-LD]</dt><dd>Manu Sporny, Gregg Kellogg, et al. <a href="http://json-ld.org/spec/latest/json-ld-syntax/"><cite>The JSON-LD Syntax</cite></a> Latest. W3C Editor's Draft. URL: <a href="http://json-ld.org/spec/latest/json-ld-syntax/">http://json-ld.org/spec/latest/json-ld-syntax/</a>
+</dd><dt id="bib-JSON-POINTER">[JSON-POINTER]</dt><dd>P. Bryan, Ed. <cite><a href="http://www.ietf.org/id/draft-pbryan-zyp-json-pointer-01.txt">JSON Pointer</a></cite> Latest. IETF Draft. URL: <a href="http://www.ietf.org/id/draft-pbryan-zyp-json-pointer-01.txt">http://www.ietf.org/id/draft-pbryan-zyp-json-pointer-01.txt</a>
+</dd><dt id="bib-RDF-CONCEPTS">[RDF-CONCEPTS]</dt><dd>Graham Klyne; Jeremy J. Carroll. <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210"><cite>Resource Description Framework (RDF): Concepts and Abstract Syntax.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210">http://www.w3.org/TR/2004/REC-rdf-concepts-20040210</a>
+</dd><dt id="bib-RFC3986">[RFC3986]</dt><dd>T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifier (URI): Generic Syntax.</cite></a> January 2005. Internet RFC 3986. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a>
+</dd><dt id="bib-RFC3987">[RFC3987]</dt><dd>M. Dürst; M. Suignard. <a href="http://www.ietf.org/rfc/rfc3987.txt"><cite>Internationalized Resource Identifiers (IRIs).</cite></a> January 2005. Internet RFC 3987. URL: <a href="http://www.ietf.org/rfc/rfc3987.txt">http://www.ietf.org/rfc/rfc3987.txt</a>
+</dd><dt id="bib-RFC4627">[RFC4627]</dt><dd>D. Crockford. <a href="http://www.ietf.org/rfc/rfc4627.txt"><cite>The application/json Media Type for JavaScript Object Notation (JSON)</cite></a> July 2006. Internet RFC 4627. URL: <a href="http://www.ietf.org/rfc/rfc4627.txt">http://www.ietf.org/rfc/rfc4627.txt</a>
+</dd><dt id="bib-WEBIDL">[WEBIDL]</dt><dd>Cameron McCormack. <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219"><cite>Web IDL.</cite></a> 19 December 2008. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219">http://www.w3.org/TR/2008/WD-WebIDL-20081219</a>
+</dd></dl></div><div id="informative-references" class="section"><h3><span class="secno">A.2 </span>Informative references</h3><dl class="bibliography"><dt id="bib-ECMA-262">[ECMA-262]</dt><dd><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm"><cite>ECMAScript Language Specification, Third Edition.</cite></a> December 1999. URL: <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">http://www.ecma-international.org/publications/standards/Ecma-262.htm</a>
+</dd><dt id="bib-MICRODATA">[MICRODATA]</dt><dd>Ian Hickson; et al. <a href="http://www.w3.org/TR/microdata/"><cite>Microdata</cite></a> 04 March 2010. W3C Working Draft. URL: <a href="http://www.w3.org/TR/microdata/">http://www.w3.org/TR/microdata/</a>
+</dd><dt id="bib-MICROFORMATS">[MICROFORMATS]</dt><dd><a href="http://microformats.org"><cite>Microformats</cite></a>. URL: <a href="http://microformats.org">http://microformats.org</a>
+</dd><dt id="bib-RDFA-CORE">[RDFA-CORE]</dt><dd>Shane McCarron; et al. <a href="http://www.w3.org/TR/2011/WD-rdfa-core-20110331"><cite>RDFa Core 1.1: Syntax and processing rules for embedding RDF through attributes.</cite></a> 31 March 2011. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2011/WD-rdfa-core-20110331">http://www.w3.org/TR/2011/WD-rdfa-core-20110331</a>
+</dd></dl></div></div></body></html>
\ No newline at end of file
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/spec/ED/json-ld-syntax/20111023/index.html Sun Oct 23 17:20:52 2011 -0700
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+
+<body style="display: inherit; "><div class="head"><p></p><h1 class="title" id="title">JSON-LD Syntax 1.0</h1><h2 id="subtitle">A Context-based JSON Serialization for Linking Data</h2><h2 id="unofficial-draft-24-october-2011">Unofficial Draft 24 October 2011</h2><dl><dt>Editor:</dt><dd><a href="http://manu.sporny.org/">Manu Sporny</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dt>Authors:</dt><dd><a href="http://digitalbazaar.com/">Manu Sporny</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dd><a href="http://digitalbazaar.com/">Dave Longley</a>, <a href="http://digitalbazaar.com/">Digital Bazaar</a></dd>
+<dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, <a href="http://kellogg-assoc.com/">Kellogg Associates</a></dd>
+<dd><a href="http://www.markus-lanthaler.com/">Markus Lanthaler</a>, <a href="http://www.tugraz.at/">Graz University of Technology</a></dd>
+<dd><a href="http://webbackplane.com/">Mark Birbeck</a>, <a href="http://webbackplane.com/">Backplane Ltd.</a></dd>
+</dl><p>This document is also available in this non-normative format: <a href="diff-20111016.html">diff to previous version</a>.</p><p class="copyright">This document is licensed under a <a class="subfoot" href="http://creativecommons.org/licenses/by/3.0/" rel="license">Creative Commons Attribution 3.0 License</a>.</p><hr /></div>
+<div id="abstract" class="introductory section"><h2>Abstract</h2>
+<p>
+JSON [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>] has proven to be a highly useful object serialization and
+messaging format. In an attempt to harmonize the representation of <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>
+in JSON, this specification outlines a common JSON representation format for
+expressing directed graphs; mixing both Linked Data and non-Linked Data in
+a single document.
+</p>
+</div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p>This document is merely a public working draft of a potential specification. It has no official standing of any kind and does not represent the support or consensus of any standards organisation.</p>
+<p>This document is an experimental work in progress.</p>
+
+<!-- <p>
+This document has been reviewed by W3C Members, by software
+developers, and by other W3C groups and interested parties, and is
+endorsed by the Director as a W3C Recommendation. It is a stable
+document and may be used as reference material or cited from another
+document. W3C's role in making the Recommendation is to draw attention
+to the specification and to promote its widespread deployment. This
+enhances the functionality and interoperability of the Web.
+</p> -->
+
+</div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a><ul class="toc"><li class="tocline"><a href="#how-to-read-this-document" class="tocxref"><span class="secno">1.1 </span>How to Read this Document</a></li><li class="tocline"><a href="#syntax-tokens-and-keywords" class="tocxref"><span class="secno">1.2 </span>Syntax Tokens and Keywords</a></li><li class="tocline"><a href="#contributing" class="tocxref"><span class="secno">1.3 </span>Contributing</a></li></ul></li><li class="tocline"><a href="#design" class="tocxref"><span class="secno">2. </span>Design</a><ul class="toc"><li class="tocline"><a href="#goals-and-rationale" class="tocxref"><span class="secno">2.1 </span>Goals and Rationale</a></li><li class="tocline"><a href="#linked-data" class="tocxref"><span class="secno">2.2 </span>Linked Data</a></li><li class="tocline"><a href="#linking-data" class="tocxref"><span class="secno">2.3 </span>Linking Data</a></li><li class="tocline"><a href="#the-context" class="tocxref"><span class="secno">2.4 </span>The Context</a><ul class="toc"><li class="tocline"><a href="#external-contexts" class="tocxref"><span class="secno">2.4.1 </span>External Contexts</a></li></ul></li><li class="tocline"><a href="#from-json-to-json-ld" class="tocxref"><span class="secno">2.5 </span>From JSON to JSON-LD</a></li></ul></li><li class="tocline"><a href="#basic-concepts" class="tocxref"><span class="secno">3. </span>Basic Concepts</a><ul class="toc"><li class="tocline"><a href="#iris" class="tocxref"><span class="secno">3.1 </span>IRIs</a></li><li class="tocline"><a href="#identifying-the-subject" class="tocxref"><span class="secno">3.2 </span>Identifying the Subject</a></li><li class="tocline"><a href="#specifying-the-type" class="tocxref"><span class="secno">3.3 </span>Specifying the Type</a></li><li class="tocline"><a href="#strings" class="tocxref"><span class="secno">3.4 </span>Strings</a></li><li class="tocline"><a href="#string-internationalization" class="tocxref"><span class="secno">3.5 </span>String Internationalization</a></li><li class="tocline"><a href="#typed-literals" class="tocxref"><span class="secno">3.6 </span>Typed Literals</a></li><li class="tocline"><a href="#multiple-objects-for-a-single-property" class="tocxref"><span class="secno">3.7 </span>Multiple Objects for a Single Property</a></li><li class="tocline"><a href="#multiple-typed-literals-for-a-single-property" class="tocxref"><span class="secno">3.8 </span>Multiple Typed Literals for a Single Property</a></li><li class="tocline"><a href="#lists" class="tocxref"><span class="secno">3.9 </span>Lists</a></li></ul></li><li class="tocline"><a href="#advanced-concepts" class="tocxref"><span class="secno">4. </span>Advanced Concepts</a><ul class="toc"><li class="tocline"><a href="#base-uri" class="tocxref"><span class="secno">4.1 </span>Base URI</a></li><li class="tocline"><a href="#default-vocabulary" class="tocxref"><span class="secno">4.2 </span>Default Vocabulary</a></li><li class="tocline"><a href="#default-language" class="tocxref"><span class="secno">4.3 </span>Default Language</a></li><li class="tocline"><a href="#vocabulary-prefixes" class="tocxref"><span class="secno">4.4 </span>Vocabulary Prefixes</a></li><li class="tocline"><a href="#automatic-typing" class="tocxref"><span class="secno">4.5 </span>Automatic Typing</a></li><li class="tocline"><a href="#type-coercion" class="tocxref"><span class="secno">4.6 </span>Type Coercion</a></li><li class="tocline"><a href="#chaining" class="tocxref"><span class="secno">4.7 </span>Chaining</a></li><li class="tocline"><a href="#identifying-unlabeled-nodes" class="tocxref"><span class="secno">4.8 </span>Identifying Unlabeled Nodes</a></li><li class="tocline"><a href="#aliasing-keywords" class="tocxref"><span class="secno">4.9 </span>Aliasing Keywords</a></li></ul></li><li class="tocline"><a href="#using-json-ld-for-rdf" class="tocxref"><span class="secno">5. </span>Using JSON-LD for RDF</a></li><li class="tocline"><a href="#markup-examples" class="tocxref"><span class="secno">A. </span>Markup Examples</a><ul class="toc"><li class="tocline"><a href="#turtle" class="tocxref"><span class="secno">A.1 </span>Turtle</a><ul class="toc"><li class="tocline"><a href="#prefix-and-base-definitions" class="tocxref"><span class="secno">A.1.1 </span>Prefix and Base definitions</a></li><li class="tocline"><a href="#chaining-1" class="tocxref"><span class="secno">A.1.2 </span>Chaining</a></li><li class="tocline"><a href="#lists-1" class="tocxref"><span class="secno">A.1.3 </span>Lists</a></li></ul></li><li class="tocline"><a href="#rdfa" class="tocxref"><span class="secno">A.2 </span>RDFa</a></li><li class="tocline"><a href="#microformats" class="tocxref"><span class="secno">A.3 </span>Microformats</a></li><li class="tocline"><a href="#microdata" class="tocxref"><span class="secno">A.4 </span>Microdata</a></li></ul></li><li class="tocline"><a href="#mashing-up-vocabularies" class="tocxref"><span class="secno">B. </span>Mashing Up Vocabularies</a></li><li class="tocline"><a href="#iana-considerations" class="tocxref"><span class="secno">C. </span>IANA Considerations</a></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">D. </span>Acknowledgements</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">E. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">E.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">E.2 </span>Informative references</a></li></ul></li></ul></div>
+
+
+
+<div id="introduction" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">1. </span>Introduction</h2>
+
+<p>
+JSON, as specified in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>], is a simple language for representing
+data on the Web. <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> is a technique for creating a graph of interlinked data across
+different
+documents or Web sites. Data entities are described using <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s,
+which are typically dereferencable and thus may be used to find more
+information about an entity, creating a "Web of Knowledge". JSON-LD is intended to be a simple
+publishing method for expressing not only Linked Data in JSON, but also for adding
+semantics to existing JSON.
+</p>
+
+<p>
+JSON-LD is designed as a light-weight syntax that can be used to express
+<a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>. It is primarily intended to be a way to use Linked Data
+in Javascript and other Web-based programming environments. It is also
+useful when building interoperable Web services and when storing Linked
+Data in JSON-based document storage engines. It is practical and designed
+to be as simple as possible, utilizing the large number of JSON parsers
+and libraries available today. It is designed to be able to
+express key-value pairs, RDF data, RDFa [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] data, Microformats
+[<cite><a class="bibref" rel="biblioentry" href="#bib-MICROFORMATS">MICROFORMATS</a></cite>] data, and Microdata [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]. That is, it supports
+every major Web-based structured data model in use today.
+</p>
+
+<p>
+The syntax does not necessarily require applications to change their JSON, but
+allows to easily add meaning by adding context in a way that is either in-band or
+out-of-band. The syntax is designed to not disturb already deployed systems
+running on JSON, but provide a smooth upgrade path from JSON to JSON with
+added semantics. Finally, the format is intended to be easy to parse, efficient to
+generate, convertible to RDF in one pass, and require a very small memory footprint
+in order to operate.
+</p>
+
+<div id="how-to-read-this-document" class="section">
+<h3><span class="secno">1.1 </span>How to Read this Document</h3>
+
+<p>
+This document is a detailed specification for a serialization of Linked
+Data in JSON. The document is primarily intended for the following audiences:
+</p>
+
+<ul>
+ <li>Web developers that want to understand the design decisions and
+ language syntax for JSON-LD.</li>
+ <li>Software developers that want to encode Microformats, RDFa, or Microdata
+ in a way that is cross-language compatible via JSON.</li>
+ <li>Software developers that want to implement processors and APIs for
+ JSON-LD.</li>
+</ul>
+
+<p>This specification does not describe the processing algorithms and programming interfaces,
+ for those see [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>].</p>
+
+<p>
+To understand the basics in this specification you must first be familiar with
+JSON, which is detailed in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>]. To understand the API and how it is
+intended to operate in a programming environment, it is useful to have working
+knowledge of the JavaScript programming language [<cite><a class="bibref" rel="biblioentry" href="#bib-ECMA-262">ECMA-262</a></cite>] and
+WebIDL [<cite><a class="bibref" rel="biblioentry" href="#bib-WEBIDL">WEBIDL</a></cite>]. To understand how JSON-LD maps to RDF, it is helpful to be
+familiar with the basic RDF concepts [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>].</p>
+
+<p>
+ Examples may contain references to existing vocabularies and use <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es to refer to Web Vocabularies. The following is a list of all vocabularies and their <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> abbreviations, as used in this document:
+</p>
+<ul>
+ <li>The <a href="http://purl.org/dc/terms/">Dublin Core</a>
+ vocabulary (abbreviation: <code>dc</code>, e.g., <code>dc:title</code>)</li>
+ <li>The <a href="http://xmlns.com/foaf/0.1/">Friend of a Friend</a>
+ vocabulary (abbreviation: <code>foaf</code>, e.g., <code>foaf:knows</code>)</li>
+ <li>The <a href="http://www.w3.org/1999/02/22-rdf-syntax-ns#">RDF</a>
+ vocabulary (abbreviation: <code>rdf</code>, e.g., <code>rdf:type</code>)</li>
+ <li>The <a href="http://www.w3.org/2001/XMLSchema#">XSD</a>
+ vocabulary (abbreviation: <code>xsd</code>, e.g., <code>xsd:integer</code>)</li>
+</ul>
+
+<p>
+ JSON [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC4627">RFC4627</a></cite>] defines several terms which are used throughout this document:
+ </p><dl>
+ <dt><dfn title="json_object" id="dfn-json_object">JSON Object</dfn></dt><dd>
+ An object structure is represented as a pair of curly brackets surrounding zero or
+ more name/value pairs (or members). A name is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>. A single colon comes after
+ each name, separating the name from the value. A single comma separates a value
+ from a following name. The names within an object <em class="rfc2119" title="should">should</em> be unique.
+ </dd>
+ <dt><dfn title="array" id="dfn-array">array</dfn></dt>
+ <dd>
+ An array is an ordered collection of values. An array structure is represented as square brackets surrounding zero or more values (or elements). Elements are separated by commas. Within JSON-LD, array order is not preserved by default, unless
+ specific markup is provided (see <a href="#lists">Lists</a>). This is because the basic data model of JSON-LD
+ is a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a>, which is inherently unordered.
+ </dd>
+ <dt><dfn title="string" id="dfn-string">string</dfn></dt><dd>
+ A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A
+ character is represented as a single character string.
+ </dd>
+ <dt><dfn title="number" id="dfn-number">number</dfn></dt>
+ <dd>
+ A number is is similar to that used in most programming languages, except that the octal and hexadecimal formats are not used and that leading zeros are not allowed.</dd>
+ <dt><dfn title="true" id="dfn-true">true</dfn> and <dfn title="false" id="dfn-false">false</dfn></dt><dd>
+ Boolean values.
+ </dd>
+ <dt><dfn title="null" id="dfn-null">null</dfn></dt><dd>
+ The use of the <em>null</em> value is undefined within JSON-LD.
+ <div class="issue">Supporting <em>null</em> in JSON-LD might have a number of advantages and should be evaluated. This is currently an <a href="https://github.com/json-ld/json-ld.org/issues/11">open issue</a>.</div>
+ </dd>
+ </dl>
+<p></p>
+
+</div>
+
+<div id="syntax-tokens-and-keywords" class="section">
+ <h3><span class="secno">1.2 </span>Syntax Tokens and Keywords</h3>
+
+ <p>JSON-LD specifies a number of syntax tokens and keywords that are using
+ in all algorithms described in this section:</p>
+
+ <dl>
+ <dt><code>@context</code></dt><dd>Used to set the <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>.</dd>
+ <dt><code>@base</code></dt><dd>Used to set the base <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> for all object IRIs affected by the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</dd>
+ <dt><code>@vocab</code></dt><dd>Used to set the base <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> for all property IRIs affected by the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</dd>
+ <dt><code>@coerce</code></dt><dd>Used to specify type coercion rules.</dd>
+ <dt><code>@literal</code></dt><dd>Used to specify a literal value.</dd>
+ <dt><code>@iri</code></dt><dd>Used to specify an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> value.</dd>
+ <dt><code>@language</code></dt><dd>Used to specify the language for a literal.</dd>
+ <dt><code>@datatype</code></dt><dd>Used to specify the datatype for a literal.</dd>
+ <dt><code>:</code></dt><dd>The separator for JSON keys and values that use the <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> mechanism.</dd>
+ <dt><code>@subject</code></dt><dd>Sets the active subject.</dd>
+ <dt><code>@type</code></dt><dd>Used to set the type of the active subject.</dd>
+ </dl>
+</div>
+
+<div id="contributing" class="section">
+<h3><span class="secno">1.3 </span>Contributing</h3>
+
+<p>There are a number of ways that one may participate in the development of
+this specification:</p>
+
+<ul>
+<li>Technical discussion typically occurs on the public mailing list:
+<a href="http://lists.w3.org/Archives/Public/public-linked-json/">public-linked-json@w3.org</a>
+</li>
+
+<li><a href="http://json-ld.org/minutes/">Public teleconferences</a> are held
+on Tuesdays at 1500UTC on the second and fourth week of each month.
+</li>
+
+<li>Specification bugs and issues should be reported in the
+<a href="https://github.com/json-ld/json-ld.org/issues">issue tracker</a>.</li>
+
+<li><a href="https://github.com/json-ld/json-ld.org/tree/master/spec">Source code</a> for the
+specification can be found on Github.</li>
+
+<li>The <a href="http://webchat.freenode.net/?channels=#json-ld">#json-ld</a>
+IRC channel is available for real-time discussion on irc.freenode.net.</li>
+</ul>
+
+</div>
+
+</div>
+
+<div id="design" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">2. </span>Design</h2>
+
+<p>The following section outlines the design goals and rationale behind the
+JSON-LD markup language.
+</p>
+
+<div id="goals-and-rationale" class="section">
+<h3><span class="secno">2.1 </span>Goals and Rationale</h3>
+
+<p>
+A number of design considerations were explored during the creation of this
+markup language:
+</p>
+
+<dl>
+ <dt>Simplicity</dt>
+ <dd>Developers need only know JSON and three keywords to use the basic
+ functionality in JSON-LD. No extra processors or software libraries are
+ necessary to use JSON-LD in its most basic form. The language attempts to
+ ensure that developers have an easy learning curve.</dd>
+ <dt>Compatibility</dt>
+ <dd>The JSON-LD markup must be 100% compatible with JSON. This ensures that
+ all of the standard JSON libraries work seamlessly with JSON-LD documents.</dd>
+ <dt>Expressiveness</dt>
+ <dd>The syntax must be able to express directed graphs, which have been proven
+ to be able to simply express almost every real world data model.</dd>
+ <dt>Terseness</dt>
+ <dd>The JSON-LD syntax must be very terse and human readable, requiring as
+ little as possible effort from the developer.</dd>
+
+<!-- <dt>Pragmatism</dt>
+ <dd>Mixing the expression of pure Linked Data with data that is not
+ linked was an approach that was driven by pragmatism. JSON-LD attempts to be
+ more practical than theoretical in its approach to Linked Data.</dd> -->
+
+ <dt>Zero Edits, most of the time</dt>
+ <dd>JSON-LD provides a mechanism that allows developers to specify
+ <a class="tref internalDFN" title="context" href="#dfn-context">context</a> in a way that is out-of-band. This allows organizations that have
+ already deployed large JSON-based infrastructure to add meaning to their
+ JSON documents in a way that is not disruptive to their day-to-day operations and is
+ transparent to their current customers. At times, mapping JSON to
+ a graph representation can become difficult. In these instances, rather than
+ having JSON-LD support esoteric markup, we chose not to support the use case
+ and support a simplified syntax instead. So, while Zero Edits is a goal,
+ it is not always possible without adding great complexity to the language.
+ </dd>
+ <dt>One-pass Processing</dt>
+ <dd>JSON-LD supports one-pass processing, which results in a very small memory
+ footprint when processing documents. For example, to convert a JSON-LD document
+ into an RDF document of any kind, only one pass is required over the data.</dd>
+</dl>
+</div>
+
+<div id="linked-data" class="section">
+<h3><span class="secno">2.2 </span>Linked Data</h3>
+<p>
+The following definition for <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> is the one that will
+be used for this specification.
+</p>
+<ol>
+ <li><dfn title="linked_data" id="dfn-linked_data">Linked Data</dfn> is a set of documents, each containing a representation of a linked data graph.</li>
+ <li>A <dfn title="linked_data_graph" id="dfn-linked_data_graph">linked data graph</dfn> is an unordered labeled directed graph, where nodes are <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>s or <a class="tref internalDFN" title="object" href="#dfn-object">object</a>s, and edges are properties.</li>
+ <li>A <dfn title="subject" id="dfn-subject">subject</dfn> is any node in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> with at least one outgoing edge.</li>
+ <li>A <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> <em class="rfc2119" title="should">should</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> (an Internationalized Resource Identifier as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>]).</li>
+ <li>An <dfn title="object" id="dfn-object">object</dfn> is a node in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> with at least one incoming edge.</li>
+ <li>An <a class="tref internalDFN" title="object" href="#dfn-object">object</a> <em class="rfc2119" title="may">may</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</li>
+ <li>An object <em class="rfc2119" title="may">may</em> be a <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> and <a class="tref internalDFN" title="object" href="#dfn-object">object</a> at the same time.</li>
+ <li>A <dfn title="property" id="dfn-property">property</dfn> is an edge of the <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a>.</li>
+ <li>A <a class="tref internalDFN" title="property" href="#dfn-property">property</a> <em class="rfc2119" title="should">should</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> that is a label in a <a class="tref internalDFN" title="linked_data_graph" href="#dfn-linked_data_graph">linked data graph</a> <em class="rfc2119" title="should">should</em> be dereferencable to a <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> document describing the labeled <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>, <a class="tref internalDFN" title="object" href="#dfn-object">object</a> or <a class="tref internalDFN" title="property" href="#dfn-property">property</a>.</li>
+ <li>A <dfn title="literal" id="dfn-literal">literal</dfn> is an <a class="tref internalDFN" title="object" href="#dfn-object">object</a> with a label that is not an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a></li>
+</ol>
+
+<p>
+Note that the definition for <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> above is silent on the
+topic of unlabeled nodes. Unlabeled nodes are not considered
+<a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>. However, this specification allows for the expression
+of unlabled nodes, as most graph-based data sets on the Web contain a number
+of associated nodes that are not named and thus are not directly
+de-referenceable.
+</p>
+</div>
+
+<div id="linking-data" class="section">
+<h3><span class="secno">2.3 </span>Linking Data</h3>
+
+<p>
+An Internationalized Resource Identifier
+(<dfn title="iri" id="dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></dfn>),
+as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3987">RFC3987</a></cite>], is a mechanism for representing unique
+identifiers on the web. In <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, an IRI is commonly
+used for expressing a <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>, a <a class="tref internalDFN" title="property" href="#dfn-property">property</a> or an
+<a class="tref internalDFN" title="object" href="#dfn-object">object</a>.
+</p>
+
+<p>JSON-LD defines a mechanism to map JSON terms, i.e., keys and values, to IRIs. This does not mean
+that JSON-LD requires every key or value to be an IRI, but rather ensures that
+keys and values can be mapped to IRIs if the developer desires to transform
+their data into <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>. There are a few techniques that can ensure
+that developers will generate good Linked Data for the Web. JSON-LD
+formalizes those techniques.
+</p>
+
+<p>We will be using the following JSON markup as the example for the
+rest of this section:
+</p>
+
+<pre class="example">{
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+</div>
+
+<div id="the-context" class="section">
+<h3><span class="secno">2.4 </span>The Context</h3>
+
+<p>In JSON-LD, a <dfn title="context" id="dfn-context">context</dfn> is used to map <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s, i.e., keys and values
+ in an JSON document, to
+ <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s. A <dfn title="term" id="dfn-term">term</dfn> is a short word that <em class="rfc2119" title="may">may</em> be expanded
+to an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>. The Web uses IRIs for unambiguous identification. The
+idea is that these <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s mean something that may be of use to
+other developers and that it is useful to give them an unambiguous identifier.
+That is, it is useful for <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s to expand to IRIs so that
+developers don't accidentally step on each other's Web Vocabulary terms.
+For example, the term <code>name</code> may map directly to the IRI
+<code>http://xmlns.com/foaf/0.1/name</code>. This allows JSON-LD documents to
+be constructed using the common JSON practice of simple name/value pairs while
+ensuring that the data is useful outside of the page, API or database in which it
+resides.
+</p>
+
+<p>These Linked Data <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s are typically collected in a context document that would look something like this:</p>
+
+<pre class="example">{
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "avatar": "http://xmlns.com/foaf/0.1/avatar"
+ }
+}</pre>
+
+<p>This context document can then be used in an JSON-LD document by adding a
+single line. The JSON markup as shown in the previous section could be changed
+as follows to link to the context document:</p>
+
+<pre class="example">{
+ <span class="diff">"@context": "http://example.org/json-ld-contexts/person",</span>
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>The additions above transform the previous JSON document into a JSON document
+with added semantics because the <code>@context</code> specifies how the
+<strong>name</strong>, <strong>homepage</strong>, and <strong>avatar</strong>
+terms map to IRIs.
+Mapping those keys to IRIs gives the data global context. If two
+developers use the same IRI to describe a property, they are more than likely
+expressing the same concept. This allows both developers to re-use each others
+data without having to agree to how their data will inter-operate on a
+site-by-site basis. Contexts may also contain datatype information
+for certain <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s as well as other processing instructions for
+the JSON-LD processor.</p>
+
+<p>Contexts may be specified in-line. This ensures that JSON-LD documents
+can be processed when a JSON-LD processor does not have access to the Web.</p>
+
+<pre class="example">{
+ <span class="diff">"@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "avatar": "http://xmlns.com/foaf/0.1/avatar"
+ },</span>
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>Contexts may be used at any time a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is defined, and a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>
+ may specify multiple contexts, to be processed in order, for example to include standard prefix
+ definitions along with a local language definition used to set the language of <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>s:</p>
+
+<p>
+ The set of contexts defined within a specific <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a> is termed a <dfn title="local_context" id="dfn-local_context">local context</dfn>.
+ The <dfn title="active_context" id="dfn-active_context">active context</dfn> refers to the accumulation of <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a>s that are in scope
+ at a specific point within the document.</p>
+
+<pre class="example">{
+ <span class="diff">"@context": [
+ "http://example.org/json-ld-contexts/person",
+ {
+ "@language": "en"
+ }
+ ],</span>
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>JSON-LD strives to ensure that developers don't have to change the JSON
+ that is going into and being returned from their Web APIs. This means
+ that developers can also specify a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> for JSON data in an out-of-band
+ fashion. This is described later in this document. </p>
+
+<p>
+ JSON-LD uses a special type of machine-readable document called a
+ <dfn title="web_vocabulary" id="dfn-web_vocabulary">Web Vocabulary</dfn> to define <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s that are then used
+ to describe concepts and "things" in the world.
+ Typically, these Web Vocabulary documents have <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es associated
+ with them and contain a number of <a class="tref internalDFN" title="term" href="#dfn-term">term</a> declarations.
+ <a class="tref internalDFN" title="prefix" href="#dfn-prefix">Prefix</a>es are helpful when a developer
+ wants to mix multiple vocabularies together in a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>, but does not want
+ to go to the trouble of defining every single term in every single vocabulary.
+ Some Web Vocabularies may have dozens of terms defined. If a developer wants to use
+ 3-4 different vocabularies, the number of terms that
+ would have to be declared in a single <a class="tref internalDFN" title="context" href="#dfn-context">context</a> could become quite large. To
+ reduce the number of different terms that must be defined, JSON-LD also allows
+ prefixes to be used to compact IRIs.
+</p><p>
+
+</p><p>For example, the <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> <code>http://xmlns.com/foaf/0.1/</code>
+specifies a <a class="tref internalDFN" title="web_vocabulary" href="#dfn-web_vocabulary">Web Vocabulary</a> which may be represented using the
+<code>foaf</code> <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>. The <code>foaf</code> Web Vocabulary
+contains a term called <strong>name</strong>. If you join the
+<code>foaf</code> <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> with the <strong>name</strong> suffix,
+you can build a compact IRI that will expand out into an absolute IRI for the
+<code>http://xmlns.com/foaf/0.1/name</code> vocabulary term.
+That is, the compact IRI, or short-form, is <code>foaf:name</code> and the
+expanded-form is <code>http://xmlns.com/foaf/0.1/name</code>. This vocabulary
+term is used to specify a person's name.
+</p>
+
+<p>Developers, and machines, are able to use this <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> (plugging it
+directly into a web browser, for instance) to go to the term and get a
+definition of what the term means. Much like we can use <a href="http://wordnet.princeton.edu/">WordNet</a> today to
+see the definition
+of words in the English language. Developers and machines need the same sort of
+definition of terms. IRIs provide a way to ensure that these terms
+are unambiguous.
+</p>
+
+<p>The <a class="tref internalDFN" title="context" href="#dfn-context">context</a> provides a collection of vocabulary <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s and
+<a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es that can be used to expand JSON keys and values into
+<a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s.</p>
+
+<p class="note">To ensure the best possible performance, it is a best practice to
+put the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition at the top of the JSON-LD document. If it isn't listed
+first, processors have to save each key-value pair until the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> is processed.
+This creates a memory and complexity burden for one-pass processors.</p>
+<div id="external-contexts" class="section">
+ <h4><span class="secno">2.4.1 </span>External Contexts</h4>
+
+ <p>Authors may choose to declare JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a>s in external
+documents to promote re-use of contexts as well as reduce the size of JSON-LD
+documents.
+In order to use an external context, an author <em class="rfc2119" title="may">may</em> specify an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> to a valid
+JSON-LD document. The referenced document <em class="rfc2119" title="must">must</em> have a top-level <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a>.
+The value of any <code>@context</code> key within that object is substituted for
+the IRI within the referencing document to have the same effect as if the value were
+specified inline within the referencing document.</p>
+ <p>The following example demonstrates the use of an external context:</p>
+
+<pre class="example">{
+ <span class="diff">"@context": "http://example.org/json-ld-contexts/person"</span>,
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>Authors may also import multiple contexts or a combination of external and local contexts by specifying a list of
+contexts:</p>
+
+<pre class="example">{
+ <span class="diff">"@context": ["http://example.org/json-ld-contexts/person", "http://example.org/json-ld-contexts/event"]</span>
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+ <span class="diff">"celebrates":
+ {
+ "@type": "Event",
+ "description": "International Talk Like a Pirate Day",
+ "date": "R/2011-09-19"
+ }</span>
+}</pre>
+
+<p>Each context in a list will be evaluated in-order. Duplicate mappings within the <a class="tref internalDFN" title="context" href="#dfn-context">context</a>s <em class="rfc2119" title="must">must</em> be
+overwritten on a last-defined-overrides basis. The context list <em class="rfc2119" title="must">must</em> contain
+either de-referenceable <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s or <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a>s that conform to the
+<a class="tref internalDFN" title="context" href="#dfn-context">context</a> syntax as described in this document.</p>
+
+<p>External JSON-LD context documents <em class="rfc2119" title="may">may</em> contain extra information located
+outside of the <code>@context</code> key, such as
+documentation about the <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es declared in the document. It is
+also <em class="rfc2119" title="recommended">recommended</em> that a human-readable document encoded in HTML+RDFa
+[<cite><a class="bibref" rel="biblioentry" href="#bib-HTML-RDFA">HTML-RDFA</a></cite>] or other Linked Data compatible format is served as well to
+explain the correct usage of the JSON-LD context document.
+</p>
+
+</div>
+
+</div>
+
+<div id="from-json-to-json-ld" class="section">
+<h3><span class="secno">2.5 </span>From JSON to JSON-LD</h3>
+
+<p>If a set of terms such as, <strong>name</strong>, <strong>homepage</strong>,
+and <strong>avatar</strong>,
+are defined in a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>, and that context is used to resolve the
+names in JSON objects, machines are able to automatically expand the terms to
+something meaningful and unambiguous, like this:</p>
+
+<pre class="example">{
+ "<span class="diff">http://xmlns.com/foaf/0.1/name</span>": "Manu Sporny",
+ "<span class="diff">http://xmlns.com/foaf/0.1/homepage</span>": "http://manu.sporny.org"
+ "<span class="diff">http://rdfs.org/sioc/ns#avatar</span>": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>Doing this allows JSON to be unambiguously machine-readable without
+requiring developers to drastically change their workflow.</p>
+<p class="note">Please note that this JSON-LD document doesn't define the
+subject and will thus result in an unlabeled or blank node.</p>
+
+</div>
+
+</div>
+
+
+
+<div id="basic-concepts" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">3. </span>Basic Concepts</h2>
+
+<p>JSON-LD is designed to ensure that <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> concepts can be marked
+up in a way that is simple to understand and author by Web developers. In many
+cases, regular JSON markup can become Linked Data with the simple addition
+of a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>. As more JSON-LD features are used, more semantics are added
+to the JSON markup.</p>
+
+<div id="iris" class="section">
+<h3><span class="secno">3.1 </span>IRIs</h3>
+
+<p>Expressing <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s are fundamental to <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> as that is how most
+<a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>s and many <a class="tref internalDFN" title="object" href="#dfn-object">object</a> are named. <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s can be
+expressed in a variety of different ways in JSON-LD.</p>
+
+<ol>
+ <li>In general, <a class="tref internalDFN" title="term" href="#dfn-term">term</a>s in the key position in
+ a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that have a mapping to an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> or another key in the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> are
+ expanded to an IRI by JSON-LD processors. There are special rules for
+ processing keys in <code>@context</code> and when dealing with keys that
+ start with the <code>@subject</code> character.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> is generated for the value specified using <code>@subject</code>,
+ if it is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> is generated for the value specified using <code>@type</code>.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> is generated for the value specified using the <code>@iri</code>
+ keyword.</li>
+ <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> is generated when there are <code>@coerce</code> rules in
+ effect for a key named <code>@iri</code>.</li>
+</ol>
+
+<p>IRIs can be expressed directly in the key position like so:
+</p>
+
+<pre class="example">{
+...
+ "<span class="diff">http://xmlns.com/foaf/0.1/name</span>": "Manu Sporny",
+...
+}</pre>
+
+<p>In the example above, the key
+<code>http://xmlns.com/foaf/0.1/name</code> is interpreted as an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>, as
+opposed to being interpreted as a string.</p>
+
+<p>Term expansion occurs for IRIs if a term is defined within the
+<a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>:</p>
+
+<pre class="example">{
+ "<span class="diff">@context</span>": {"<span class="diff">name</span>": "<span class="diff">http://xmlns.com/foaf/0.1/name</span>"},
+...
+ "<span class="diff">name</span>": "Manu Sporny",
+...
+}</pre>
+
+<p><a class="tref internalDFN" title="prefix" href="#dfn-prefix">Prefix</a>es are expanded when used in keys:</p>
+
+<pre class="example">{
+ "<span class="diff">@context</span>": {"<span class="diff">foaf</span>": "<span class="diff">http://xmlns.com/foaf/0.1/</span>"},
+...
+ "<span class="diff">foaf:name</span>": "Manu Sporny",
+...
+}</pre>
+
+<p><code>foaf:name</code> above will automatically expand out to the IRI
+<code>http://xmlns.com/foaf/0.1/name</code>.</p>
+
+<p>An <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> is generated when a value is associated with a key using
+the <code>@iri</code> keyword:</p>
+
+<pre class="example">{
+...
+ "homepage": { "<span class="diff">@iri</span>": "http://manu.sporny.org" }
+...
+}</pre>
+
+<p>If type coercion rules are specified in the <code>@context</code> for
+a particular vocabulary term, an IRI is generated:</p>
+
+<pre class="example">{<span class="diff">
+ "@context":
+ {
+ ...
+ "@coerce":
+ {
+ "@iri": "homepage"
+ }
+ }</span>
+...
+ "homepage": "http://manu.sporny.org/",
+...
+}</pre>
+
+<p>Even though the value <code>http://manu.sporny.org/</code> is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>,
+the type coercion rules will transform the value into an IRI when processed
+by a JSON-LD Processor</p>
+
+<p>IRIs may be represented as an absolute IRI, a <a class="tref internalDFN" title="term" href="#dfn-term">term</a>, a <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>:<a class="tref internalDFN" title="term" href="#dfn-term">term</a> construct, or as a value relative to <code>@base</code> or <code>@vocab</code>.</p>
+
+</div>
+
+<div id="identifying-the-subject" class="section">
+<h3><span class="secno">3.2 </span>Identifying the Subject</h3>
+
+<p>
+ To be able to externally reference nodes, it is important that each node has an unambiguous identifier.
+ <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s are a fundamental concept of <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, and nodes should have a de-referencable
+ identifier used to name and locate them. For nodes to be truely linked, de-referencing the identifier
+ should result in a representation of that node. Associating an IRI with a node tells an application
+ that the returned document contains a description of the node requested.
+</p>
+<p>
+ JSON-LD documents may also contain descriptions of other nodes, so it is necessary to be able to
+ uniquely identify each node which may be externally referenced.
+</p>
+<p>A <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>
+ of an object in JSON is declared using the <code>@subject</code> key. The subject is the
+first piece of information needed by the JSON-LD processor in order to
+create the (subject, property, object) tuple, also known as a triple.</p>
+
+<pre class="example">{
+...
+ "<span class="diff">@subject</span>": "<span class="diff">http://example.org/people#joebob</span>",
+...
+}</pre>
+
+<p>The example above would set the subject to the IRI
+<code>http://example.org/people#joebob</code>.
+</p>
+
+<p class="note">To ensure the best possible performance, it is a best practice to
+put the <code>@subject</code> key before other key-value pairs in an object. If
+it isn't listed first, processors have to save each key-value pair until
+<code>@subject</code> is processed before they can create valid triples. This
+creates a memory and complexity burden for one-pass processors.</p>
+
+</div>
+
+<div id="specifying-the-type" class="section">
+<h3><span class="secno">3.3 </span>Specifying the Type</h3>
+
+<p>The type of a particular subject can be specified using the
+<code>@type</code> key. Specifying the type in this way will generate a
+triple of the form (subject, type, type-iri).</p>
+
+<p>To be <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, types <em class="rfc2119" title="must">must</em> be uniquely identified by an
+ <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</p>
+
+<pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "<span class="diff">@type</span>": "<span class="diff">http://xmlns.com/foaf/0.1/Person</span>",
+...
+}</pre>
+
+<p>The example above would generate the following triple if the JSON-LD
+document is mapped to RDF (in N-Triples notation):</p>
+
+<pre class="example"><http://example.org/people#joebob>
+ <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
+ <http://xmlns.com/foaf/0.1/Person> .</pre>
+
+</div>
+
+<div id="strings" class="section">
+<h3><span class="secno">3.4 </span>Strings</h3>
+
+<p>Regular text strings, also referred to as <dfn title="plain_literal" id="dfn-plain_literal">plain literal</dfn>s, are
+easily expressed using regular JSON <a class="tref internalDFN" title="string" href="#dfn-string">string</a>s.</p>
+
+<pre class="example">{
+...
+ "name": "<span class="diff">Mark Birbeck</span>",
+...
+}</pre>
+
+</div>
+
+<div id="string-internationalization" class="section">
+<h3><span class="secno">3.5 </span>String Internationalization</h3>
+
+<p>JSON-LD makes an assumption that strings with associated language encoding
+information are not very common when used in JavaScript and Web Services.
+Thus, it takes a little more effort to express strings with associated
+language information.</p>
+
+<pre class="example">{
+...
+ "name": <span class="diff">
+ {
+ "@literal": "花澄",
+ "@language": "ja"
+ }</span>
+...
+}</pre>
+
+<p>The example above would generate a <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a> for
+<em>花澄</em> and associate the <code>ja</code> language code with the triple
+that is generated. Languages <em class="rfc2119" title="must">must</em> be expressed in [<cite><a class="bibref" rel="biblioentry" href="#bib-BCP47">BCP47</a></cite>] format.</p>
+
+<p>It is also possible to set a language to use within a <code>@context</code>, to allow specify a language
+to apply to all <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>s within the scope of the <a class="tref internalDFN" title="context" href="#dfn-context">context</a></p>
+
+<pre class="example">{
+ <span class="diff">"@context:" {
+ "@language": "ja"
+ },</span>
+...
+ "name": <span class="diff">"花澄"</span>
+...
+}</pre>
+</div>
+
+<div id="typed-literals" class="section">
+<h3><span class="secno">3.6 </span>Typed Literals</h3>
+
+<p>
+ A value with an associated datatype, also known as a
+ <dfn title="typed_literal" id="dfn-typed_literal">typed literal</dfn>, is indicated by associating a literal with
+ an <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> which indicates the literal's datatype. Typed literals may be
+ expressed in JSON-LD in three ways:
+</p>
+
+<ol>
+ <li>By utilizing the <code>@coerce</code> keyword.</li>
+ <li>By utilizing the expanded form for specifying objects.</li>
+ <li>By using a native JSON datatype.</li>
+</ol>
+
+<p>The first example uses the <code>@coerce</code> keyword to express a
+typed literal:</p>
+
+<pre class="example">{<span class="diff">
+ "@context":
+ {
+ "modified": "http://purl.org/dc/terms/modified",
+ "dateTime": "http://www.w3.org/2001/XMLSchema#dateTime"
+ "@coerce":
+ {
+ "dateTime": "modified"
+ }
+ }</span>
+...
+ "modified": "2010-05-29T14:17:39+02:00",
+...
+}</pre>
+
+<p>The second example uses the expanded form for specifying objects:</p>
+
+<pre class="example">{
+...
+ "modified": <span class="diff">
+ {
+ "@literal": "2010-05-29T14:17:39+02:00",
+ "@datatype": "dateTime"
+ }</span>
+...
+}</pre>
+
+<p>Both examples above would generate an object with the literal value of
+<code>2010-05-29T14:17:39+02:00</code> and the datatype of
+<code>http://www.w3.org/2001/XMLSchema#dateTime</code>.</p>
+
+<p>The third example uses a built-in native JSON type, a
+ <a class="tref internalDFN" title="number" href="#dfn-number">number</a>, to express a datatype:</p>
+
+<pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "age": <span class="diff">31</span>
+...
+}</pre>
+
+<p>The example above would generate the following triple:</p>
+
+<pre class="example"><http://example.org/people#joebob>
+ <http://xmlns.com/foaf/0.1/age>
+ "31"^^<http://www.w3.org/2001/XMLSchema#integer> .</pre>
+
+</div>
+
+<div id="multiple-objects-for-a-single-property" class="section">
+<h3><span class="secno">3.7 </span>Multiple Objects for a Single Property</h3>
+
+<p>A JSON-LD author can express multiple triples in a compact way by using
+<a class="tref internalDFN" title="array" href="#dfn-array">array</a>s. If a subject has multiple values for the same property, the author
+<em class="rfc2119" title="may">may</em> express each property as an <a class="tref internalDFN" title="array" href="#dfn-array">array</a>.</p>
+
+<p class="note">In JSON-LD, multiple objects on a property are not ordered. This is because typically graphs
+are not inherently ordered data structures. To see more on creating ordered collections
+in JSON-LD, see <a href="#lists">Lists</a>.
+</p>
+
+<pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "nick": <span class="diff">["joe", "bob", "jaybee"]</span>,
+...
+}</pre>
+
+<p>The markup shown above would generate the following triples:</p>
+
+<pre class="example"><http://example.org/people#joebob>
+ <http://xmlns.com/foaf/0.1/nick>
+ "joe" .
+<http://example.org/people#joebob>
+ <http://xmlns.com/foaf/0.1/nick>
+ "bob" .
+<http://example.org/people#joebob>
+ <http://xmlns.com/foaf/0.1/nick>
+ "jaybee" .</pre>
+
+</div>
+
+<div id="multiple-typed-literals-for-a-single-property" class="section">
+<h3><span class="secno">3.8 </span>Multiple Typed Literals for a Single Property</h3>
+
+<p>Multiple <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a>s may also be expressed using the expanded
+form for objects:</p>
+
+<pre class="example">{
+...
+ "@subject": "http://example.org/articles/8",
+ "modified": <span class="diff">
+ [
+ {
+ "@literal": "2010-05-29T14:17:39+02:00",
+ "@datatype": "dateTime"
+ },
+ {
+ "@literal": "2010-05-30T09:21:28-04:00",
+ "@datatype": "dateTime"
+ }
+ ]</span>
+...
+}</pre>
+
+<p>The markup shown above would generate the following triples:</p>
+
+<pre class="example"><http://example.org/articles/8>
+ <http://purl.org/dc/terms/modified>
+ "2010-05-29T14:17:39+02:00"^^http://www.w3.org/2001/XMLSchema#dateTime .
+<http://example.org/articles/8>
+ <http://purl.org/dc/terms/modified>
+ "2010-05-30T09:21:28-04:00"^^http://www.w3.org/2001/XMLSchema#dateTime .</pre>
+
+</div>
+
+<div id="lists" class="section">
+ <h3><span class="secno">3.9 </span>Lists</h3>
+ <p>
+ Because graphs do not describe ordering for links between nodes, in contrast to plain JSON, multi-valued properties
+ in JSON-LD do not provide an ordering of the listed objects. For example, consider the following
+ simple document:
+ </p>
+ <pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "nick": <span class="diff">["joe", "bob", "jaybee"]</span>,
+...
+}</pre>
+ <p>
+ This results in three triples being generated, each relating the subject to an individual
+ object, with no inherent order.</p>
+ <p>To preserve the order of the objects, RDF-based languages, such as [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>]
+ use the concept of an <code>rdf:List</code> (as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>]). This uses a sequence
+ of unlabeled nodes with properties describing a value, a null-terminated next property. Without
+ specific syntactical support, this could be represented in JSON-LD as follows:
+ </p>
+ <pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "nick": <span class="diff">{</span>,
+ <span class="diff">"@first": "joe"</span>,
+ <span class="diff">"@rest": {</span>
+ <span class="diff">"@first": "bob"</span>,
+ <span class="diff">"@rest": {</span>
+ <span class="diff">"@first": "jaybee"</span>,
+ <span class="diff">"@rest": "@nil"</span>
+ <span class="diff">}</span>
+ <span class="diff">}</span>
+ <span class="diff">}</span>
+ <span class="diff">}</span>,
+...
+}</pre>
+ <p>
+ As this notation is rather unwieldy and the notion of ordered collections is rather important
+ in data modeling, it is useful to have specific language support. In JSON-LD, a list may
+ be represented using the <code>@list</code> keyword as follows:
+ </p>
+ <pre class="example">{
+...
+ "@subject": "http://example.org/people#joebob",
+ "foaf:nick": <span class="diff">{"@list": ["joe", "bob", "jaybee"]}</span>,
+...
+}</pre>
+ <p>
+ This describes the use of this <a class="tref internalDFN" title="array" href="#dfn-array">array</a> as being ordered, and order is maintained through normalization
+ and RDF conversion as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>]. If every use of a given multi-valued property is a list, this
+ may be abbreviated by adding an <code>@coerce</code> term:
+ </p>
+ <pre class="example">{
+ <span class="diff">"@context": {</span>
+ ...
+ <span class="diff">"@coerce": {</span>
+ <span class="diff">"@list": ["foaf:nick"]</span>
+ <span class="diff">}</span>
+ <span class="diff">}</span>,
+...
+ "@subject": "http://example.org/people#joebob",
+ "foaf:nick": <span class="diff">["joe", "bob", "jaybee"]</span>,
+...
+}</pre>
+ <p>
+ The @list keyword can be used within the <code>@coerce</code> section of a <code>@context</code> to
+ cause value arrays to be coerced into an ordered list.
+ </p>
+</div>
+
+</div>
+
+<div id="advanced-concepts" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">4. </span>Advanced Concepts</h2>
+
+<p>JSON-LD has a number of features that provide functionality above and beyond
+the core functionality described above. The following sections outline the
+features that are specific to JSON-LD.
+</p>
+
+
+<div id="base-uri" class="section">
+<h3><span class="secno">4.1 </span>Base URI</h3>
+<p>JSON-LD allows <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s to be specified in a relative form. For <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a> and <a class="tref internalDFN" title="object" href="#dfn-object">object</a>
+ IRIs, relative IRIs are resolved against the document base using
+ <cite><a href="http://www.ietf.org/rfc/rfc2396.txt">section 5.1 Establishing a
+ Base URI</a></cite> of [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3986">RFC3986</a></cite>]. This value may be explicitly
+ set with a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> using the <code>@base</code> keyword.</p>
+
+<p>For example, if a JSON-LD document was retrieved from <code>http://manu.sporny.org/</code>,
+ relative IRIs would resolve against that URI:</p>
+
+<pre class="example">{
+ <span class="diff">"@subject": "about/"</span>,
+ "http://xmlns.com/foaf/0.1/name": "Manu Sporny",
+ "http://xmlns.com/foaf/0.1/homepage: ""
+}</pre>
+
+<p>This document uses an empty <code>@subject</code>, which resolves to the document base. However, if
+ the document is moved to a different location, the subject IRI would change. To prevent this, a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>
+ may have a <code>@base</code> mapping, to set an absolute base for the document in spite of where
+ it actually is retrieved from. It <em class="rfc2119" title="must">must</em> have a value of a simple
+ <a class="tref internalDFN" title="string" href="#dfn-string">string</a> with the lexical form of an absolute <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</p>
+
+<pre class="example">{
+ <span class="diff">"@context": { "@base": "http://manu.sporny.org/"}</span>,
+ "@subject": "about/",
+ "http://xmlns.com/foaf/0.1/name": "Manu Sporny",
+ "http://xmlns.com/foaf/0.1/homepage: ""
+}</pre>
+</div>
+
+<div id="default-vocabulary" class="section">
+<h3><span class="secno">4.2 </span>Default Vocabulary</h3>
+<p>It is often common that all types and properties come from the same vocabulary. JSON-LD provides
+ a way to set a base URI to be used for all properties and types that aren't based on terms,
+ prefixes or absolute IRIs. Much like the <code>@base</code> keyword, the <code>@vocab</code> keyword
+ can be used to set a base <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> to use for all types and properties that don't otherwise resolve to
+ an absolute <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.
+
+</p><pre class="example">{
+ <span class="diff">"@context": { "@vocab": "http://xmlns.com/foaf/1.0/" },</span>
+ <span class="diff">"@type": "Person"</span>,
+ "name": "Manu Sporny",
+ "homepage": "http://manu.sporny.org/",
+ "avatar": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+</div>
+
+<div id="default-language" class="section">
+<h3><span class="secno">4.3 </span>Default Language</h3>
+<p>JSON-LD allows a default value to use as the language for <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>s.
+ It is commonly the case that documents are written using a single language. As described in
+ <a href="string-internationalization">String Internationalization</a>, a language-tagged literal
+ may be specified as follows:</p>
+
+<pre class="example">{
+...
+ "name":
+ {
+ "@literal": "花澄",
+ "@language": "ja"
+ }
+...
+}</pre>
+
+<p>By specifying <code>@language</code> within a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>, multiple language-tagged literals may be
+ marked up using a simple string form:</p>
+</div>
+
+<pre class="example">{
+ <span class="diff">"@context": { "@language": "ja"}</span>,
+...
+ "name": <span class="diff">"花澄"</span>
+...
+}</pre>
+<div id="vocabulary-prefixes" class="section">
+ <h3><span class="secno">4.4 </span>Vocabulary Prefixes</h3>
+ <p>
+ Vocabulary terms in <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> documents may draw from a number of
+ different Web vocabularies. At times, declaring every single term that
+ a document uses can require the developer to declare tens, if not
+ hundreds of potential vocabulary terms that may be used across an
+ application. This is a concern for at least three reasons; the
+ first is the cognitive load on the developer, the second is
+ the serialized size of the <a class="tref internalDFN" title="context" href="#dfn-context">context</a>, the third is future-proofing
+ application contexts. In order to address these issues, the concept of a
+ <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> mechanism is introduced.</p>
+ <p>
+ A <dfn title="prefix" id="dfn-prefix">prefix</dfn> is a compact way of expressing a base
+ <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a> to a <a class="tref internalDFN" title="web_vocabulary" href="#dfn-web_vocabulary">Web Vocabulary</a>.
+ Generally, these prefixes are used by concatenating the <em>prefix</em> and
+ a <em>suffix</em> separated by a colon (<code>:</code>).
+ The <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> is a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> taken from the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>,
+ a short string that identifies a particular Web vocabulary.
+ For example, the prefix <code>foaf</code> may be used as a short
+ hand for the Friend-of-a-Friend Web Vocabulary, which is identified using
+ the IRI <code>http://xmlns.com/foaf/0.1/</code>. A developer may append any of
+ the FOAF Vocabulary terms to the end of the prefix to specify a short-hand
+ version of the absolute IRI for the vocabulary term. For example,
+ <code>foaf:name</code> would be expanded out to the IRI
+ <code>http://xmlns.com/foaf/0.1/name</code>. Instead of having to remember
+ and type out the entire IRI, the developer can instead use the prefix in
+ their JSON-LD markup.
+ </p>
+ <p>
+ The ability to use <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>es reduces the need for developers
+ to declare every vocabulary term that they intend to use in
+ the JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a>. This reduces document serialization size because
+ every vocabulary term need not be declared in the context.
+ <a class="tref internalDFN" title="prefix" href="#dfn-prefix">Prefix</a> also
+ reduce the cognitive load on the developer. It is far easier to
+ remember <code>foaf:name</code> than it is to remember
+ <code>http://xmlns.com/foaf/0.1/name</code>. The use of prefixes also
+ ensures that a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> document does not have to be updated in lock-step
+ with an externally defined <a class="tref internalDFN" title="web_vocabulary" href="#dfn-web_vocabulary">Web Vocabulary</a>. Without prefixes, a developer
+ would need to keep their application context terms in lock-step with an
+ externally defined Web Vocabulary. Rather, by just declaring the
+ Web Vocabulary prefix, one can use new terms as they're declared
+ without having to update the application's JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a>.
+ </p>
+ <p>Consider the following example:</p>
+ <pre class="example">{
+ "@context": {
+ <span class="diff">"dc": "http://purl.org/dc/elements/1.1/",</span>
+ <span class="diff">"ex": "http://example.org/vocab#"</span>
+ },
+ "@subject": "http://example.org/library",
+ "@type": <span class="diff">"ex:Library"</span>,
+ <span class="diff">"ex:contains"</span>: {
+ "@subject": "http://example.org/library/the-republic",
+ "@type": <span class="diff">"ex:Book"</span>,
+ <span class="diff">"dc:creator"</span>: "Plato",
+ <span class="diff">"dc:title"</span>: "The Republic",
+ <span class="diff">"ex:contains"</span>: {
+ "@subject": "http://example.org/library/the-republic#introduction",
+ "@type": <span class="diff">"ex:Chapter"</span>,
+ <span class="diff">"dc:description"</span>: "An introductory chapter on The Republic.",
+ <span class="diff">"dc:title"</span>: "The Introduction"
+ },
+ },
+}</pre>
+ <p>
+ In this example, two different vocabularies are referred to using
+ prefixes. Those prefixes are then used as type and property values using
+ the <code>prefix:suffix</code> notation.
+ </p>
+ <p>
+ Prefixes, also known as CURIEs, are defined more formally in RDFa Core 1.1,
+ <cite><a href="http://www.w3.org/TR/rdfa-core/#s_curies">Section 6
+ "CURIE Syntax Definition"</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>].
+ JSON-LD does not support the square-bracketed CURIE syntax as the
+ mechanism is not required to disambiguate <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s in a JSON-LD document like
+ it is in HTML documents.
+ </p>
+</div>
+
+<div id="automatic-typing" class="section">
+<h3><span class="secno">4.5 </span>Automatic Typing</h3>
+
+<p>Since JSON is capable of expressing typed information such as doubles,
+integers, and boolean values. As demonstrated below, JSON-LD utilizes that
+information to create <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a>s:</p>
+
+<pre class="example">{
+...
+ // The following two values are automatically converted to a type of xsd:double
+ // and both values are equivalent to each other.
+ "measure:cups": <span class="diff">5.3</span>,
+ "measure:cups": <span class="diff">5.3e0</span>,
+ // The following value is automatically converted to a type of xsd:double as well
+ "space:astronomicUnits": <span class="diff">6.5e73</span>,
+ // The following value should never be converted to a language-native type
+ "measure:stones": <span class="diff">{ "@literal": "4.8", "@datatype": "xsd:decimal" }</span>,
+ // This value is automatically converted to having a type of xsd:integer
+ "chem:protons": <span class="diff">12</span>,
+ // This value is automatically converted to having a type of xsd:boolean
+ "sensor:active": <span class="diff">true</span>,
+...
+}</pre>
+
+<p class="note">When dealing with a number of modern programming languages,
+including JavaScript ECMA-262, there is no distinction between
+<strong>xsd:decimal</strong> and <strong>xsd:double</strong> values. That is,
+the <a class="tref internalDFN" title="number" href="#dfn-number">number</a> <code>5.3</code> and the <a class="tref internalDFN" title="number" href="#dfn-number">number</a>
+<code>5.3e0</code> are treated as if they were the same. When converting from
+JSON-LD to a language-native format and back, datatype information is lost in a
+number of these languages. Thus, one could say that <code>5.3</code> is a
+<strong>xsd:decimal</strong> and <code>5.3e0</code> is an
+<strong>xsd:double</strong> in JSON-LD, but when both values are
+converted to a language-native format the datatype difference between the two
+is lost because the machine-level representation will almost always be a
+<strong>double</strong>.
+Implementers should be aware of this potential round-tripping issue between
+<strong>xsd:decimal</strong> and <strong>xsd:double</strong>. Specifically
+objects with a datatype of <strong>xsd:decimal</strong> <em class="rfc2119" title="must not">must not</em> be converted
+to a language native type.
+</p>
+
+</div>
+
+<div id="type-coercion" class="section">
+<h3><span class="secno">4.6 </span>Type Coercion</h3>
+
+<p>JSON-LD supports the coercion of values to particular data types.
+Type coercion allows someone deploying JSON-LD to coerce the incoming or
+outgoing types to the proper data type based on a mapping of data type <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s to
+property types. Using type coercion, one may convert simple JSON data to
+properly typed RDF data.</p>
+
+<p>The example below demonstrates how a JSON-LD author can coerce values to
+<a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a>s, <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a>s and IRIs.</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+ "xsd": "http://www.w3.org/2001/XMLSchema#",
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "age": "http://xmlns.com/foaf/0.1/age",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+<span class="diff"> "@coerce":
+ {
+ "xsd:integer": "age",
+ "@iri": "homepage"
+ }</span>
+ },
+ "name": "John Smith",
+ "age": <span class="diff">"41"</span>,
+ "homepage": <span class="diff">"http://example.org/home/"</span>
+}</pre>
+
+<p>The example above would generate the following triples:</p>
+
+<pre class="example">_:bnode1
+ <http://xmlns.com/foaf/0.1/name>
+ "John Smith" .
+_:bnode1
+ <http://xmlns.com/foaf/0.1/age>
+ "41"^^http://www.w3.org/2001/XMLSchema#integer .
+_:bnode1
+ <http://xmlns.com/foaf/0.1/homepage>
+ <http://example.org/home/> .</pre>
+
+<div class="issue">
+ <p>The mechanism for type coercion is still being debated. It may be that the key/value
+ positions are swapped, yielding a <code>@context</code> such as the following:</p>
+
+<pre class="example">{
+ "@context": {
+ "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+ "xsd": "http://www.w3.org/2001/XMLSchema#",
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "age": "http://xmlns.com/foaf/0.1/age",
+ "homepage": "http://xmlns.com/foaf/0.1/homepage",
+ "currentProject": "http://xmlns.com/foaf/0.1/currentProject",
+ <span class="diff">"@coerce": {
+ "age": "xsd:integer",
+ "homepage": "@iri",
+ "currentProject": ["@iri", "@list"]
+ }</span>
+ },
+ ...
+}</pre>
+
+<p>An alternative is to merge the coercion into term definitions:</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+ "xsd": "http://www.w3.org/2001/XMLSchema#",
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "age": <span class="diff">{"@iri": "http://xmlns.com/foaf/0.1/age", "@coerce": "xsd:integer"}</span>,
+ "homepage": <span class="diff">{"@iri": "http://xmlns.com/foaf/0.1/age", "@coerce": "@iri"}</span>,
+ "currentProject": <span class="diff">{"@iri": "http://xmlns.com/foaf/0.1/currentProject", "@coerce": ["@iri", "@list"]}</span>,
+ },
+ ...
+}</pre>
+</div>
+
+</div>
+
+<div id="chaining" class="section">
+ <h3><span class="secno">4.7 </span>Chaining</h3>
+ <p>
+ Object <dfn title="chaining" id="dfn-chaining">chaining</dfn> is a JSON-LD feature that allows an author to
+ use the definition of JSON-LD objects as <a class="tref internalDFN" title="property" href="#dfn-property">property</a> values. This
+ is a commonly used mechanism for creating a parent-child relationship
+ between two <a class="tref internalDFN" title="subject" href="#dfn-subject">subject</a>s.
+ </p>
+ <p>The example shows an two subjects related by a property from the first
+ subject:</p>
+
+ <pre class="example">{
+...
+ "name": "Manu Sporny",
+ "<span class="diff">knows</span>": {
+ "<span class="diff">@type</span>": "<span class="diff">Person</span>",
+ "<span class="diff">name</span>": "<span class="diff">Gregg Kellogg</span>",
+ }
+...
+}</pre>
+
+ <p>
+ An object definition, like the one used above, <em class="rfc2119" title="may">may</em> be used as a
+ JSON value at any point in JSON-LD.
+ </p>
+</div>
+
+<div id="identifying-unlabeled-nodes" class="section">
+<h3><span class="secno">4.8 </span>Identifying Unlabeled Nodes</h3>
+
+<p>At times, it becomes necessary to be able to express information without
+being able to specify the subject. Typically, this type of node is called
+an unlabeled node or a blank node. In JSON-LD, unlabeled node identifiers are
+automatically created if a subject is not specified using the
+<code>@subject</code> keyword. However, authors may provide identifiers for
+unlabeled nodes by using the special <code>_</code> (underscore)
+<a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>. This allows to reference the node locally within the
+document but not in an external document.</p>
+
+<pre class="example">{
+...
+ "@subject": "<span class="diff">_:foo</span>",
+...
+}</pre>
+
+<p>The example above would set the subject to <code>_:foo</code>, which can
+then be used later on in the JSON-LD markup to refer back to the
+unlabeled node. This practice, however, is usually frowned upon when
+generating <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>. If a developer finds that they refer to the unlabeled
+node more than once, they should consider naming the node using a resolve-able
+<a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.
+</p>
+
+</div>
+
+<div id="aliasing-keywords" class="section">
+<h3><span class="secno">4.9 </span>Aliasing Keywords</h3>
+
+<p>JSON-LD allows all of the syntax keywords, except for <code>@context</code>,
+to be aliased. This feature allows more legacy JSON content to be supported
+by JSON-LD. It also allows developers to design domain-specific implementations
+using only the JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a>.</p>
+
+<pre class="example">{
+ "@context":
+ {
+ <span class="diff">"url": "@subject"</span>,
+ <span class="diff">"a": "@type"</span>,
+ "name": "http://schema.org/name"
+ },
+ "url": "http://example.com/about#gregg",
+ "a": "http://schema.org/Person",
+ "name": "Gregg Kellogg"
+}</pre>
+
+<p>In the example above, the <code>@subject</code> and <code>@type</code>
+keywords have been given the aliases <strong>url</strong> and
+<strong>a</strong>, respectively.
+</p>
+
+</div>
+
+</div>
+
+<div id="using-json-ld-for-rdf" class="section">
+
+<!-- OddPage -->
+<h2><span class="secno">5. </span>Using JSON-LD for RDF</h2>
+
+ <p>JSON-LD is a specification for representing <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> in JSON. A common
+ way of working with Linked Data is through <dfn title="rdf" id="dfn-rdf">RDF</dfn>, the Resource Description Framework.
+ RDF can be expressed using JSON-LD by associating JSON-LD concepts such as <code>@subject</code>
+ and <code>@type</code> with the equivalent <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>s in RDF. Further information about
+ RDF may be found in [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-PRIMER">RDF-PRIMER</a></cite>].</p>
+
+ <p>Some examples of encoding <a class="tref internalDFN" title="rdf" href="#dfn-rdf">RDF</a> into JSON-LD may be found
+ in <a href="#markup-examples">Appendix A</a>. Details of transforming JSON-LD into RDF
+ are defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>].</p>
+</div>
+
+<div class="appendix section" id="markup-examples">
+
+<!-- OddPage -->
+<h2><span class="secno">A. </span>Markup Examples</h2>
+
+<p>The JSON-LD markup examples below demonstrate how JSON-LD can be used to
+ express semantic data marked up in other languages such as RDFa, Microformats,
+ and Microdata. These sections are merely provided as proof that JSON-LD is
+ very flexible in what it can express across different <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> approaches.</p>
+
+<div id="turtle" class="section">
+ <h3><span class="secno">A.1 </span>Turtle</h3>
+
+ <p>The following are examples of representing <a class="tref internalDFN" title="rdf" href="#dfn-rdf">RDF</a> as expressed in [<cite><a class="bibref" rel="biblioentry" href="#bib-TURTLE">TURTLE</a></cite>] into JSON-LD.</p>
+
+<div id="prefix-and-base-definitions" class="section">
+<h4><span class="secno">A.1.1 </span>Prefix and Base definitions</h4>
+<p>The JSON-LD context has direct equivalents for Turtle <code>@base</code> and <code>@prefix</code> expressions:</p>
+
+<pre class="example">@base <http://manu.sporny.org/> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+
+<#me> a foaf:Person;
+ foaf:name "Manu Sporny";
+ foaf:homepage <> .</pre>
+
+<pre class="example">{
+ "@context": {
+ "@base": "http://manu.sporny.org/",
+ "foaf": "http://xmlns.com/foaf/0.1/"
+ },
+ "@subject": "#me",
+ "@type": "foaf:Person",
+ "foaf:name": "Manu Sporny",
+ "foaf:homepage": {"@iri": ""}
+}</pre>
+</div>
+
+<div id="chaining-1" class="section">
+<h4><span class="secno">A.1.2 </span>Chaining</h4>
+<p>Both Turtle and JSON-LD allow chaining of objects, although Turtle only allows chaining of objects which
+ use nlank node identifiers.</p>
+</div>
+
+<pre class="example">@base <http://manu.sporny.org/> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+
+<#me> a foaf:Person;
+ foaf:name "Manu Sporny";
+ foaf:knows [ a foaf:Person; foaf:name "Gregg Kellogg" ] .</pre>
+
+<pre class="example">{
+ "@context": {
+ "@base": "http://manu.sporny.org/",
+ "foaf": "http://xmlns.com/foaf/0.1/"
+ },
+ "@subject": "#me",
+ "@type": "foaf:Person",
+ "foaf:name": "Manu Sporny",
+ "foaf:knows": {
+ "@type": "foaf:Person",
+ "foaf:name": "Gregg Kellogg"
+ }
+}</pre>
+<div id="lists-1" class="section">
+<h4><span class="secno">A.1.3 </span>Lists</h4>
+<p>Both JSON-LD and Turtle can represent sequential lists of values.</p>
+
+<pre class="example">@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+
+<http://example.org/people#joebob> a foaf:Person;
+ foaf:name "Joe Bob";
+ foaf:nick ( "joe" "bob" "jaybee") .</pre>
+
+<pre class="example">{
+ "@context": {
+ "@base": "http://manu.sporny.org/",
+ "foaf": "http://xmlns.com/foaf/0.1/"
+ },
+ "@subject": "http://example.org/people#joebob",
+ "@type": "foaf:Person",
+ "foaf:name": "Joe Bob",
+ "foaf:nick": {"@list": ["joe", "bob", "jaybe"]}
+}</pre>
+</div>
+
+</div>
+
+<div id="rdfa" class="section">
+<h3><span class="secno">A.2 </span>RDFa</h3>
+
+<p>The following example describes three people with their respective names and
+homepages.</p>
+
+<pre class="example"><div <span class="diff">prefix="foaf: http://xmlns.com/foaf/0.1/"</span>>
+ <ul>
+ <li <span class="diff">typeof="foaf:Person"</span>>
+ <a <span class="diff">rel="foaf:homepage" href="http://example.com/bob/" property="foaf:name" </span>>Bob</a>
+ </li>
+ <li <span class="diff">typeof="foaf:Person"</span>>
+ <a <span class="diff">rel="foaf:homepage" href="http://example.com/eve/" property="foaf:name" </span>>Eve</a>
+ </li>
+ <li <span class="diff">typeof="foaf:Person"</span>>
+ <a <span class="diff">rel="foaf:homepage" href="http://example.com/manu/" property="foaf:name" </span>>Manu</a>
+ </li>
+ </ul>
+</div></pre>
+
+<p>An example JSON-LD implementation is described below, however, there are
+other ways to mark-up this information such that the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> is not
+repeated.</p>
+
+<pre class="example">{
+ "@context": { "foaf": "http://xmlns.com/foaf/0.1/"},
+ "@subject": [
+ {
+ "@subject": "_:bnode1",
+ "@type": "foaf:Person",
+ "foaf:homepage": "http://example.com/bob/",
+ "foaf:name": "Bob"
+ },
+ {
+ "@subject": "_:bnode2",
+ "@type": "foaf:Person",
+ "foaf:homepage": "http://example.com/eve/",
+ "foaf:name": "Eve"
+ },
+ {
+ "@subject": "_:bnode3",
+ "@type": "foaf:Person",
+ "foaf:homepage": "http://example.com/manu/",
+ "foaf:name": "Manu"
+ }
+ ]
+}</pre>
+
+</div>
+
+<div id="microformats" class="section">
+<h3><span class="secno">A.3 </span>Microformats</h3>
+
+<p>The following example uses a simple Microformats hCard example to express
+how the Microformat is represented in JSON-LD.</p>
+
+<pre class="example"><div class="vcard">
+ <a class="url fn" href="http://tantek.com/">Tantek Çelik</a>
+</div></pre>
+
+<p>The representation of the hCard expresses the Microformat terms in the
+<a class="tref internalDFN" title="context" href="#dfn-context">context</a> and uses them directly for the <code>url</code> and <code>fn</code>
+properties. Also note that the Microformat to JSON-LD processor has
+generated the proper URL type for <code>http://tantek.com</code>.</p>
+
+<pre class="example">{
+ "@context":
+ {
+ "vcard": "http://microformats.org/profile/hcard#vcard",
+ "url": "http://microformats.org/profile/hcard#url",
+ "fn": "http://microformats.org/profile/hcard#fn",
+ "@coerce": { "@iri": "url" }
+ },
+ "@subject": "_:bnode1",
+ "@type": "vcard",
+ "url": "http://tantek.com/",
+ "fn": "Tantek Çelik"
+}</pre>
+
+</div>
+
+<div id="microdata" class="section">
+<h3><span class="secno">A.4 </span>Microdata</h3>
+
+<p>The Microdata example below expresses book information as a Microdata Work
+item.
+</p>
+
+<pre class="example"><dl itemscope
+ itemtype="http://purl.org/vocab/frbr/core#Work"
+ itemid="http://purl.oreilly.com/works/45U8QJGZSQKDH8N">
+ <dt>Title</dt>
+ <dd><cite itemprop="http://purl.org/dc/terms/title">Just a Geek</cite></dd>
+ <dt>By</dt>
+ <dd><span itemprop="http://purl.org/dc/terms/creator">Wil Wheaton</span></dd>
+ <dt>Format</dt>
+ <dd itemprop="http://purl.org/vocab/frbr/core#realization"
+ itemscope
+ itemtype="http://purl.org/vocab/frbr/core#Expression"
+ itemid="http://purl.oreilly.com/products/9780596007683.BOOK">
+ <link itemprop="http://purl.org/dc/terms/type" href="http://purl.oreilly.com/product-types/BOOK">
+ Print
+ </dd>
+ <dd itemprop="http://purl.org/vocab/frbr/core#realization"
+ itemscope
+ itemtype="http://purl.org/vocab/frbr/core#Expression"
+ itemid="http://purl.oreilly.com/products/9780596802189.EBOOK">
+ <link itemprop="http://purl.org/dc/terms/type" href="http://purl.oreilly.com/product-types/EBOOK">
+ Ebook
+ </dd>
+</dl></pre>
+
+<p>Note that the JSON-LD representation of the Microdata information stays
+true to the desires of the Microdata community to avoid contexts and
+instead refer to items by their full <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>.</p>
+
+<pre class="example">[
+ {
+ "@subject": "http://purl.oreilly.com/works/45U8QJGZSQKDH8N",
+ "@type": "http://purl.org/vocab/frbr/core#Work",
+ "http://purl.org/dc/terms/title": "Just a Geek",
+ "http://purl.org/dc/terms/creator": "Whil Wheaton",
+ "http://purl.org/vocab/frbr/core#realization":
+ ["http://purl.oreilly.com/products/9780596007683.BOOK", "http://purl.oreilly.com/products/9780596802189.EBOOK"]
+ },
+ {
+ "@subject": "http://purl.oreilly.com/products/9780596007683.BOOK",
+ "@type": "http://purl.org/vocab/frbr/core#Expression",
+ "http://purl.org/dc/terms/type": "http://purl.oreilly.com/product-types/BOOK"
+ },
+ {
+ "@subject": "http://purl.oreilly.com/products/9780596802189.EBOOK",
+ "@type": "http://purl.org/vocab/frbr/core#Expression",
+ "http://purl.org/dc/terms/type": "http://purl.oreilly.com/product-types/EBOOK"
+ }
+]</pre>
+</div>
+</div>
+
+<div class="appendix section" id="mashing-up-vocabularies">
+
+<!-- OddPage -->
+<h2><span class="secno">B. </span>Mashing Up Vocabularies</h2>
+
+<p>Developers would also benefit by allowing other vocabularies to be used
+automatically with their JSON API. There are over 200
+<a class="tref internalDFN" title="web_vocabulary" href="#dfn-web_vocabulary">Web Vocabulary</a> Documents that are available for use on the Web
+today. Some of these vocabularies are:
+</p>
+
+<ul>
+ <li>RDF - for describing information about objects and concepts on the Web.</li>
+ <li>RDFS - for expressing things like labels and comments.</li>
+ <li>XSD - for specifying basic types like strings, integers, dates and times.</li>
+ <li>Dublin Core - for describing creative works.</li>
+ <li>FOAF - for describing social networks.</li>
+ <li>Calendar - for specifying events.</li>
+ <li>SIOC - for describing discussions on blogs and websites.</li>
+ <li>CCrel - for describing Creative Commons and other types of licenses.</li>
+ <li>GEO - for describing geographic location.</li>
+ <li>VCard - for describing organizations and people.</li>
+ <li>DOAP - for describing projects.</li>
+</ul>
+
+<p>You can use these vocabularies in combination, like so:</p>
+
+<pre class="example">{
+ "<span class="diff">@type</span>": "<span class="diff">foaf:Person</span>",
+ "<span class="diff">foaf:name</span>": "Manu Sporny",
+ "<span class="diff">foaf:homepage</span>": "http://manu.sporny.org/",
+ "<span class="diff">sioc:avatar</span>": "http://twitter.com/account/profile_image/manusporny"
+}</pre>
+
+<p>Developers can also specify their own Vocabulary documents by modifying the
+<a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> in-line using the <code>@context</code> keyword,
+like so:</p>
+
+<pre class="example">{
+ <span class="diff">"@context": { "myvocab": "http://example.org/myvocab#" }</span>,
+ "@type": "foaf:Person",
+ "foaf:name": "Manu Sporny",
+ "foaf:homepage": "http://manu.sporny.org/",
+ "sioc:avatar": "http://twitter.com/account/profile_image/manusporny"<span class="diff">,
+ "myvocab:personality": "friendly"</span>
+}</pre>
+
+<p>The <code>@context</code> keyword is used to change how the JSON-LD
+processor evaluates key-value pairs. In this case, it was used to
+map one string ('myvocab') to another string, which is interpreted as
+a <a class="tref internalDFN" title="iri" href="#dfn-iri">IRI</a>. In the example above, the <code>myvocab</code> string is replaced
+with "<code>http://example.org/myvocab#</code>" when it
+is detected. In the example above, "<code>myvocab:personality</code>" would
+expand to "<code>http://example.org/myvocab#personality</code>".</p>
+
+<p>This mechanism is a short-hand, called a <a class="tref internalDFN" title="web_vocabulary" href="#dfn-web_vocabulary">Web Vocabulary</a> <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>,
+and provides developers an unambiguous way to map any JSON value to RDF.</p><p>
+
+</p></div>
+
+<div class="appendix section" id="iana-considerations">
+
+<!-- OddPage -->
+<h2><span class="secno">C. </span>IANA Considerations</h2>
+
+<p>This section is included merely for standards community review and will be
+submitted to the Internet Engineering Steering Group if this specification
+becomes a W3C Recommendation.</p>
+
+<dl>
+ <dt>Type name:</dt>
+ <dd>application</dd>
+ <dt>Subtype name:</dt>
+ <dd>ld+json</dd>
+ <dt>Required parameters:</dt>
+ <dd>None</dd>
+ <dt>Optional parameters:</dt>
+ <dd>
+ <dl>
+ <dt><code>form</code></dt>
+ <dd>Determines the serialization form for the JSON-LD document. Valid
+ values include; <code>compacted</code>, <code>expanded</code>,
+ <code>framed</code>, and <code>normalized</code>. Other values are
+ allowed, but must be pre-pended with a <code>x-</code> string until
+ they are clearly defined by a stable specification. If no form
+ is specified in an HTTP request header to a responding application,
+ such as a Web server, the application <em class="rfc2119" title="may">may</em> choose any form. If no
+ form is specified for a receiving application, the form <em class="rfc2119" title="must not">must not</em>
+ be assumed to take any particular form.</dd>
+ <div class="issue">It is currently <a href="https://github.com/json-ld/json-ld.org/issues/14"> being discussed to remove form=framed</a> from this specification as there are several issues with it.</div>
+ </dl>
+ </dd>
+ <dt>Encoding considerations:</dt>
+ <dd>The same as the <code>application/json</code> MIME media type.</dd>
+ <dt>Security considerations:</dt>
+ <dd>Since JSON-LD is intended to be a pure data exchange format for
+ directed graphs, the serialization <em class="rfc2119" title="should not">should not</em> be passed through a
+ code execution mechanism such as JavaScript's <code>eval()</code>
+ function. It is <em class="rfc2119" title="recommended">recommended</em> that a conforming parser does not attempt to
+ directly evaluate the JSON-LD serialization and instead purely parse the
+ input into a language-native data structure. </dd>
+ <dt>Interoperability considerations:</dt>
+ <dd>Not Applicable</dd>
+ <dt>Published specification:</dt>
+ <dd>The <a href="http://json-ld/spec/latest/">JSON-LD</a> specification.</dd>
+ <dt>Applications that use this media type:</dt>
+ <dd>Any programming environment that requires the exchange of
+ directed graphs. Implementations of JSON-LD have been created for
+ JavaScript, Python, Ruby, PHP and C++.
+ </dd>
+ <dt>Additional information:</dt>
+ <dd>
+ <dl>
+ <dt>Magic number(s):</dt>
+ <dd>Not Applicable</dd>
+ <dt>File extension(s):</dt>
+ <dd>.jsonld</dd>
+ <dt>Macintosh file type code(s):</dt>
+ <dd>TEXT</dd>
+ </dl>
+ </dd>
+ <dt>Person & email address to contact for further information:</dt>
+ <dd>Manu Sporny <msporny@digitalbazaar.com></dd>
+ <dt>Intended usage:</dt>
+ <dd>Common</dd>
+ <dt>Restrictions on usage:</dt>
+ <dd>None</dd>
+ <dt>Author(s):</dt>
+ <dd>Manu Sporny, Gregg Kellogg, Dave Longley</dd>
+ <dt>Change controller:</dt>
+ <dd>W3C</dd>
+</dl>
+
+</div>
+
+<div class="appendix section" id="acknowledgements">
+
+<!-- OddPage -->
+<h2><span class="secno">D. </span>Acknowledgements</h2>
+
+<p>The editors would like to thank Mark Birbeck, who provided a great deal of
+the initial push behind the JSON-LD work via his work on RDFj,
+Dave Longley, Dave Lehn and Mike Johnson who reviewed, provided feedback, and
+performed several implementations of the specification, and Ian Davis, who
+created RDF/JSON. Thanks also to Nathan Rixham, Bradley P. Allen,
+Kingsley Idehen, Glenn McDonald, Alexandre Passant, Danny Ayers, Ted
+Thibodeau Jr., Olivier Grisel, Niklas Lindström, Markus Lanthaler, and Richard
+Cyganiak for their input on the specification.
+</p>
+</div>
+
+
+
+<div id="respec-err" style="position: fixed; width: 350px; top: 10px; right: 10px; border: 3px double #f00; background: #fff" class="removeOnSave"><ul><li style="color: #c00">There appears to have been a problem fetching the style sheet; status=0</li></ul></div><div id="references" class="appendix section">
+<!-- OddPage -->
+<h2><span class="secno">E. </span>References</h2><div id="normative-references" class="section"><h3><span class="secno">E.1 </span>Normative references</h3><dl class="bibliography"><dt id="bib-BCP47">[BCP47]</dt><dd>A. Phillips, M. Davis. <a href="http://tools.ietf.org/rfc/bcp/bcp47.txt"><cite>Tags for Identifying Languages</cite></a> September 2009. IETF Best Current Practice. URL: <a href="http://tools.ietf.org/rfc/bcp/bcp47.txt">http://tools.ietf.org/rfc/bcp/bcp47.txt</a>
+</dd><dt id="bib-RDF-CONCEPTS">[RDF-CONCEPTS]</dt><dd>Graham Klyne; Jeremy J. Carroll. <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210"><cite>Resource Description Framework (RDF): Concepts and Abstract Syntax.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210">http://www.w3.org/TR/2004/REC-rdf-concepts-20040210</a>
+</dd><dt id="bib-RFC3987">[RFC3987]</dt><dd>M. Dürst; M. Suignard. <a href="http://www.ietf.org/rfc/rfc3987.txt"><cite>Internationalized Resource Identifiers (IRIs).</cite></a> January 2005. Internet RFC 3987. URL: <a href="http://www.ietf.org/rfc/rfc3987.txt">http://www.ietf.org/rfc/rfc3987.txt</a>
+</dd><dt id="bib-RFC4627">[RFC4627]</dt><dd>D. Crockford. <a href="http://www.ietf.org/rfc/rfc4627.txt"><cite>The application/json Media Type for JavaScript Object Notation (JSON)</cite></a> July 2006. Internet RFC 4627. URL: <a href="http://www.ietf.org/rfc/rfc4627.txt">http://www.ietf.org/rfc/rfc4627.txt</a>
+</dd><dt id="bib-WEBIDL">[WEBIDL]</dt><dd>Cameron McCormack. <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219"><cite>Web IDL.</cite></a> 19 December 2008. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219">http://www.w3.org/TR/2008/WD-WebIDL-20081219</a>
+</dd></dl></div><div id="informative-references" class="section"><h3><span class="secno">E.2 </span>Informative references</h3><dl class="bibliography"><dt id="bib-ECMA-262">[ECMA-262]</dt><dd><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm"><cite>ECMAScript Language Specification, Third Edition.</cite></a> December 1999. URL: <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">http://www.ecma-international.org/publications/standards/Ecma-262.htm</a>
+</dd><dt id="bib-HTML-RDFA">[HTML-RDFA]</dt><dd>Manu Sporny; et al. <a href="http://www.w3.org/TR/rdfa-in-html/"><cite>HTML+RDFa</cite></a> 04 March 2010. W3C Working Draft. URL: <a href="http://www.w3.org/TR/rdfa-in-html/">http://www.w3.org/TR/rdfa-in-html/</a>
+</dd><dt id="bib-JSON-LD-API">[JSON-LD-API]</dt><dd>Manu Sporny, Gregg Kellogg, Dave Longley, Eds. <cite><a href="http://json-ld.org/spec/latest/json-ld-api/">JSON-LD API</a></cite> Latest. W3C Editor's Draft. URL: <a href="http://json-ld.org/spec/latest/json-ld-api/">http://www.w3.org/2010/02/rdfa/sources/rdf-interfaces/</a>
+</dd><dt id="bib-MICRODATA">[MICRODATA]</dt><dd>Ian Hickson; et al. <a href="http://www.w3.org/TR/microdata/"><cite>Microdata</cite></a> 04 March 2010. W3C Working Draft. URL: <a href="http://www.w3.org/TR/microdata/">http://www.w3.org/TR/microdata/</a>
+</dd><dt id="bib-MICROFORMATS">[MICROFORMATS]</dt><dd><a href="http://microformats.org"><cite>Microformats</cite></a>. URL: <a href="http://microformats.org">http://microformats.org</a>
+</dd><dt id="bib-RDF-PRIMER">[RDF-PRIMER]</dt><dd>Frank Manola; Eric Miller. <a href="http://www.w3.org/TR/2004/REC-rdf-primer-20040210/"><cite>RDF Primer.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-primer-20040210/">http://www.w3.org/TR/2004/REC-rdf-primer-20040210/</a>
+</dd><dt id="bib-RDF-SCHEMA">[RDF-SCHEMA]</dt><dd>Dan Brickley; Ramanathan V. Guha. <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210"><cite>RDF Vocabulary Description Language 1.0: RDF Schema.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210">http://www.w3.org/TR/2004/REC-rdf-schema-20040210</a>
+</dd><dt id="bib-RDFA-CORE">[RDFA-CORE]</dt><dd>Shane McCarron; et al. <a href="http://www.w3.org/TR/2011/WD-rdfa-core-20110331"><cite>RDFa Core 1.1: Syntax and processing rules for embedding RDF through attributes.</cite></a> 31 March 2011. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2011/WD-rdfa-core-20110331">http://www.w3.org/TR/2011/WD-rdfa-core-20110331</a>
+</dd><dt id="bib-RFC3986">[RFC3986]</dt><dd>T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifier (URI): Generic Syntax.</cite></a> January 2005. Internet RFC 3986. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a>
+</dd><dt id="bib-TURTLE">[TURTLE]</dt><dd>David Beckett, Tim Berners-Lee. <a href="http://www.w3.org/TeamSubmission/turtle/"><cite>Turtle: Terse RDF Triple Language.</cite></a> January 2008. W3C Team Submission. URL: <a href="http://www.w3.org/TeamSubmission/turtle/">http://www.w3.org/TeamSubmission/turtle/</a>
+</dd></dl></div></div></body></html>
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