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@@ -0,0 +1,2222 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>JSON-LD Algorithms 1.0</title>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
+<!--
+ === NOTA BENE ===
+ For the three scripts below, if your spec resides on dev.w3 you can check them
+ out in the same tree and use relative links so that they'll work offline,
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+ // if you wish the publication date to be other than today, set this
+ //publishDate: "2012-12-25",
+ copyrightStart: "2010",
+
+ // the specification's short name, as in http://www.w3.org/TR/short-name/
+ shortName: "json-ld-api",
+ subtitle: "Algorithms for Processing JSON-LD Documents",
+
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+
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+
+ // editors, add as many as you like
+ // only "name" is required
+ editors: [
+ { name: "Manu Sporny", url: "http://manu.sporny.org/",
+ company: "Digital Bazaar", companyURL: "http://digitalbazaar.com/" },
+ { name: "Gregg Kellogg", url: "http://greggkellogg.net/",
+ company: "Kellogg Associates", companyURL: "http://kellogg-assoc.com/" },
+ { name: "Markus Lanthaler", url: "http://www.markus-lanthaler.com/",
+ company: "Graz University of Technology", companyURL: "http://www.tugraz.at/" }
+ ],
+
+ // authors, add as many as you like.
+ // This is optional, uncomment if you have authors as well as editors.
+ // only "name" is required. Same format as editors.
+
+ authors: [
+ { name: "Dave Longley", url: "http://digitalbazaar.com/",
+ company: "Digital Bazaar", companyURL: "http://digitalbazaar.com/"},
+ { name: "Manu Sporny", url: "http://digitalbazaar.com/",
+ company: "Digital Bazaar", companyURL: "http://digitalbazaar.com/" },
+ { name: "Gregg Kellogg", url: "http://greggkellogg.net/",
+ company: "Kellogg Associates", companyURL: "http://kellogg-assoc.com/" },
+ { name: "Markus Lanthaler", url: "http://www.markus-lanthaler.com/",
+ company: "Graz University of Technology", companyURL: "http://www.tugraz.at/" }
+ ],
+
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+
+ // URI of the public WG page
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+
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+
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+ // This is important for Rec-track documents, do not copy a patent URI from a random
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+</style>
+</head>
+
+<body>
+<section id="abstract">
+<p>
+JSON [[!RFC4627]] has proven to be a highly useful object serialization and
+messaging format. JSON-LD [[!JSON-LD]] 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 in order to make them easier to work with in programming
+environments like JavaScript, Python, and Ruby.
+</p>
+</section>
+
+<section id='sotd'>
+<p>This document has been under development for over 18 months in the
+JSON for Linking Data Community Group. The document has recently been
+transferred to the RDF Working Group for review, improvement, and publication
+along the Recommendation track. The specification has undergone significant
+development, review, and changes during the course of the last 18 months.
+</p>
+<p>There are several independent
+<a href="http://json-ld.org/#impl">interoperable implementations</a> of
+this specification. There is
+a <a href="https://github.com/json-ld/json-ld.org/tree/master/test-suite">fairly complete test suite</a>
+and a <a href="http://json-ld.org/playground/">live JSON-LD editor</a>
+that is capable of demonstrating the features described in
+this document. While development on implementations, the test suite
+and the live editor will continue, they are believed to be mature enough
+to be integrated into a non-production system at this point in time with
+the expectation that they could be used in a production system within the
+next year.
+</p>
+<p class="issue">
+It is important for readers to understand that the scope of this document is
+currently under debate and new features may be added to the specification.
+Existing features may be modified heavily or removed entirely from the
+specification upon further review and feedback from the broader community.
+This is a work in progress and publication as a Working Draft
+does not require that all Working Group members agree on the content of the
+document.
+</p>
+
+<p>There are a number of ways that one may participate in the development of
+ this specification:</p>
+
+<ul>
+ <li>If you want to make sure that your feedback is formally addressed by
+ the RDF Working Group, you should send it to public-rdf-comments:
+ <a href="http://lists.w3.org/Archives/Public/public-rdf-comments/">public-rdf-comments@w3.org</a></li>
+
+ <li>Ad-hoc technical discussion primarily occurs on the public community 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 JSON-LD Community Group teleconferences</a>
+ are held on Tuesdays at 1500UTC every week. Participation is open to the
+ public.</li>
+
+ <li>RDF Working Group teleconferences are held on Wednesdays at 1500UTC
+ every week. Participation is limited to RDF Working Group members.</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>
+ if you do not want to send an e-mail to the public-rdf-comments mailing
+ list.</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>
+
+</section>
+
+<section class="informative">
+<h2>Introduction</h2>
+
+<p>
+This document is a detailed specification for an Application Programming
+Interface for the JSON-LD Syntax. The document is primarily intended for
+the following audiences:
+</p>
+
+<ul>
+ <li>Web authors and developers that want a very detailed view of how
+ a JSON-LD processor and the API operates.</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 [[!RFC4627]]. You must also understand the
+JSON-LD Syntax [[!JSON-LD]], 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 [[ECMA-262]] and
+WebIDL [[!WEBIDL]]. To understand how JSON-LD maps to RDF, it is helpful to be
+familiar with the basic RDF concepts [[!RDF-CONCEPTS]].</p>
+
+</section>
+
+<section class="informative">
+<h1>Features</h1>
+
+<p>The JSON-LD Syntax specification [[!JSON-LD]] outlines a language that may be
+ used to express Linked Data in JSON. Often, it is useful to be able to transform
+ JSON-LD documents so that they may be easily processed in various programming
+ environments.</p>
+
+<p>There are four major types of transformation that are discussed in this document:
+ expansion, compaction, flattening, and RDF conversion.</p>
+
+<section class="informative">
+ <h2>Expansion</h2>
+ <p>Software algorithms are easiest to write when the data that they are processing
+ have a regular form. Since information can be represented by JSON-LD in a
+ variety of different ways, transforming all of these methods into a uniform
+ structure allows the developer to simplify their processing code. For example,
+ note that the following input uses only <tref>term</tref>s and is fairly
+ compact:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": {
+ "@id": "http://xmlns.com/foaf/0.1/homepage",
+ "@type": "@id"
+ }
+ },
+ "@id": "http://me.markus-lanthaler.com/",
+ "name": "Markus Lanthaler",
+ "homepage": "http://www.markus-lanthaler.com/"
+ }
+ -->
+ </pre>
+
+ <p>The next input example uses one <tref>IRI</tref> to express a property, but leaves
+ the rest of the information untouched.</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "homepage": {
+ "@id": "http://xmlns.com/foaf/0.1/homepage",
+ "@type": "@id"
+ }
+ },
+ "@id": "http://me.markus-lanthaler.com/",
+ "****http://xmlns.com/foaf/0.1/name****": "Markus Lanthaler",
+ "homepage": "http://www.markus-lanthaler.com/"
+ }
+ -->
+ </pre>
+
+ <p>While both inputs are valid JSON-LD, writing a program to handle every
+ permutation of possible inputs can be difficult, especially when the incoming
+ context could change as well. To ensure that the data can be given a more
+ uniform structure, JSON-LD introduces the notion of expansion. <tdef>Expansion</tdef>
+ performs two important operations. The first is to expand all values that represent
+ <tref title="IRI">IRIs</tref> to <tref title="absolute IRI">absolute IRIs</tref>.
+ The second is to express all values in <tref>expanded form</tref>. Running the
+ <a href="#expansion-algorithm">Expansion algorithm</a> against the examples provided
+ above results in the following output:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ [
+ {
+ "@id": "http://me.markus-lanthaler.com/",
+ "http://xmlns.com/foaf/0.1/name": [
+ { "@value": "Markus Lanthaler" }
+ ],
+ "http://xmlns.com/foaf/0.1/homepage": [
+ { "@id": "http://www.markus-lanthaler.com/" }
+ ]
+ }
+ ]
+ -->
+ </pre>
+
+ <p>Note that in the output above all <tref>context</tref> definitions have
+ been removed, all <tref title="term">terms</tref> and <tref title="prefix">prefixes</tref>
+ have been expanded to absolute <tref title="IRI">IRIs</tref>, and all
+ <tref title="JSON-LD value">JSON-LD values</tref> are expressed in <tref>expanded form</tref>.
+ While the output is more difficult for a human to read, it is easier for a
+ software program to process because of its very regular structure.</p>
+</section>
+
+<section class="informative">
+ <h2>Compaction</h2>
+ <p>While expansion expands a given input as much as possible, compaction performs
+ the opposite operation: it expresses a given input as succinctly as possible. In contrast
+ to expansion which is meant to produce something that is easy to process by software
+ programs, compaction is meant to produce something that is easy to read by software
+ developers. Compaction uses a developer-supplied <tref>context</tref> to compress
+ <tref title="IRI">IRIs</tref> to <tref title="term">terms</tref> or
+ <tref title="compact IRI">compact IRIs</tref> and <tref title="JSON-LD value">JSON-LD values</tref>
+ expressed in <tref>expanded form</tref> to simple values such as
+ <tref title="string">strings</tref> and <tref title="number">numbers</tref>.</p>
+
+ <p>For example, assume the following expanded JSON-LD input document:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ [
+ {
+ "@id": "http://me.markus-lanthaler.com/",
+ "http://xmlns.com/foaf/0.1/name": [
+ { "@value": "Markus Lanthaler" }
+ ],
+ "http://xmlns.com/foaf/0.1/homepage": [
+ { "@id": "http://www.markus-lanthaler.com/" }
+ ]
+ }
+ ]
+ -->
+ </pre>
+
+ <p>Additionally, assume the following developer-supplied JSON-LD <tref>context</tref>:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": {
+ "@id": "http://xmlns.com/foaf/0.1/homepage",
+ "@type": "@id"
+ }
+ }
+ }
+ -->
+ </pre>
+
+ <p>Running the <a href="#compaction-algorithm">Compaction Algorithm</a> given the context
+ supplied above against the JSON-LD input document provided above would result in the
+ following output:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "homepage": {
+ "@id": "http://xmlns.com/foaf/0.1/homepage",
+ "@type": "@id"
+ }
+ },
+ "@id": "http://me.markus-lanthaler.com/",
+ "name": "Markus Lanthaler",
+ "homepage": "http://www.markus-lanthaler.com/"
+ }
+ -->
+ </pre>
+
+ <p>Note that all <tref title="IRI">IRIs</tref> have been compacted to
+ <tref title="term">terms</tref> as specified in the <tref>context</tref>
+ which consequently has been injected into the output. While compacted
+ output is most useful to humans, it can often also be used to generate
+ structures that are easy to program against. Compaction enables developers
+ to map any expanded document into an application-specific compacted document.
+ While the context provided above mapped <code>http://xmlns.com/foaf/0.1/name</code>
+ to <code>name</code>, it could have also have been mapped to any other term
+ provided by the developer.</p>
+
+</section>
+
+<section class="informative">
+ <h2>Flattening</h2>
+ <p>While expansion ensures that a document is in a uniform structure, flattening
+ goes a step further and ensures that also the shape of the data is deterministic.
+ In expanded documents properties of a single <tref>node</tref> may still be
+ spread across a number of different <tref title="JSON object">JSON objects</tref>.
+ By flattening a document, all properties of a <tref>node</tref> are collected in a
+ single <tref>JSON object</tref> and all <tref title="blank node">blank nodes</tref>
+ are labeled with a <tref>blank node identifier</tref>. Often this drastically
+ simplifies the code to process JSON-LD data.</p>
+
+ <p>For example, assume the following JSON-LD input document:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "knows": "http://xmlns.com/foaf/0.1/knows"
+ },
+ "@id": "http://me.markus-lanthaler.com/",
+ "name": "Markus Lanthaler",
+ "knows": [
+ {
+ "name": "Manu Sporny",
+ "knows": {
+ "@id": "http://greggkellogg.net/foaf#me"
+ }
+ },
+ {
+ "@id": "http://greggkellogg.net/foaf#me",
+ "name": "Gregg Kellogg"
+ }
+ ]
+ }
+ -->
+ </pre>
+
+ <p>Running the <a href="#flattening-algorithm">Flattening Algorithm</a>
+ with a context set to <tref>null</tref> to prevent compaction returns
+ the following document:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ [
+ {
+ "@id": "http://me.markus-lanthaler.com/",
+ "http://xmlns.com/foaf/0.1/name": [
+ { "@value": "Markus Lanthaler" }
+ ],
+ "http://xmlns.com/foaf/0.1/knows": [
+ { "@id": "_:t0" },
+ { "@id": "http://greggkellogg.net/foaf#me" }
+ ]
+ },
+ {
+ "@id": "_:t0",
+ "http://xmlns.com/foaf/0.1/name": [
+ { "@value": "Manu Sporny" }
+ ],
+ "http://xmlns.com/foaf/0.1/knows": [
+ { "@id": "http://greggkellogg.net/foaf#me" }
+ ]
+ },
+ {
+ "@id": "http://greggkellogg.net/foaf#me",
+ "http://xmlns.com/foaf/0.1/name": [
+ { "@value": "Gregg Kellogg" }
+ ]
+ }
+ ]
+ -->
+ </pre>
+
+ <p>Note how in the output above all properties of a <tref>node</tref> are collected in a
+ single <tref>JSON object</tref> and how the <tref>blank node</tref> representing
+ "Manu Sporny" has been assigned the <tref>blank node identifier</tref>
+ <code>_:t0</code>.</p>
+
+ <p>To make it easier for humans to read such a flattened document can be compacted by
+ passing a context. Using the same context as the input document, the flattened
+ and compacted document looks as follows:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ {
+ "@context": {
+ "name": "http://xmlns.com/foaf/0.1/name",
+ "knows": "http://xmlns.com/foaf/0.1/knows"
+ },
+ "@graph": [
+ {
+ "@id": "http://me.markus-lanthaler.com/",
+ "name": "Markus Lanthaler",
+ "knows": [
+ { "@id": "_:t0" },
+ { "@id": "http://greggkellogg.net/foaf#me" }
+ ]
+ },
+ {
+ "@id": "_:t0",
+ "name": "Manu Sporny",
+ "knows": {
+ "@id": "http://greggkellogg.net/foaf#me"
+ }
+ },
+ {
+ "@id": "http://greggkellogg.net/foaf#me",
+ "name": "Gregg Kellogg"
+ }
+ ]
+ }
+ -->
+ </pre>
+
+ <p>Please note that the flattened and compacted result will always explicitly
+ designate the default by the <code>@graph</code> member in the top-level
+ <tref>JSON object</tref>. <a href="#compaction">Compaction</a> optimizes that
+ member away if its value contains just one item.</p>
+</section>
+
+<section class="informative">
+ <h2>RDF Conversion</h2>
+ <p>JSON-LD can be used to serialize data expressed in RDF as described in
+ [[RDF-CONCEPTS]]. This ensures that data can be round-tripped from and to
+ any RDF syntax without any loss in the fidelity of the data.</p>
+
+ <p>For example, assume the following RDF input serialized in Turtle [[TURTLE-TR]]:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ <http://me.markus-lanthaler.com/> <http://xmlns.com/foaf/0.1/name> "Markus Lanthaler" .
+ <http://me.markus-lanthaler.com/> <http://xmlns.com/foaf/0.1/homepage> <http://www.markus-lanthaler.com/> .
+ -->
+ </pre>
+
+ <p>Using the <a href="#convert-from-rdf-algorithm">Convert from RDF Algorithm</a> a
+ developer could transform this document into expanded JSON-LD:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ [
+ {
+ "@id": "http://me.markus-lanthaler.com/",
+ "http://xmlns.com/foaf/0.1/name": [
+ {
+ "@value": "Markus Lanthaler"
+ }
+ ],
+ "http://xmlns.com/foaf/0.1/homepage": [
+ {
+ "@id": "http://www.markus-lanthaler.com/"
+ }
+ ]
+ }
+ ]
+ -->
+ </pre>
+
+ <p>Note that the output above could easily be compacted using the technique outlined
+ in the previous section. It is also possible to transform the JSON-LD document back
+ to RDF using the <a href="#convert-to-rdf-algorithm">Convert to RDF Algorithm</a>.</p>
+ </section>
+
+</section>
+
+<section>
+ <h2>Conformance</h2>
+
+ <p>All examples and notes as well as sections marked as non-normative in this
+ specification are non-normative. Everything else in this specification is
+ normative.</p>
+
+ <p>The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+ MAY, and OPTIONAL in this specification are to be interpreted as described
+ in [[!RFC2119]].</p>
+
+ <p>There are two classes of products that can claim conformance to this
+ specification: <tref title="JSON-LD Implementation">JSON-LD Implementations</tref>
+ and <tref title="JSON-LD Processor">JSON-LD Processors</tref>.</p>
+
+ <p>A conforming <tdef>JSON-LD Implementation</tdef> is a system capable of transforming
+ JSON-LD documents according the algorithms defined in this specification.</p>
+
+ <p>A conforming <tdef>JSON-LD Processor</tdef> is a conforming <tref>JSON-LD Implementation</tref>
+ that exposes the application programming interface (API) defined in this specification.</p>
+
+ <p>The algorithms in this specification are generally written with more concern for clarity than
+ over efficiency. Thus, JSON-LD Implementations and Processors may implement the algorithms
+ given in this specification in any way desired, so long as the end result is indistinguishable
+ from the result that would be obtained by the specification's algorithms.</p>
+
+ <p>This specification does not define how JSON-LD Implementations or Processors handle
+ non-conforming input documents. This implies that JSON-LD Implementations or Processors
+ MUST NOT attempt to correct malformed IRIs or language tags; however, they MAY issue
+ validation warnings.</p>
+
+ <p class="note">Implementers can partially check their level of conformance to
+ this specification by successfully passing the test cases of the JSON-LD test
+ suite [[JSON-LD-TESTS]]. Note, however, that passing all the tests in the test
+ suite does not imply complete conformance to this specification. It only implies
+ that the implementation conforms to aspects tested by the test suite.</p>
+</section>
+
+<section>
+ <h3>General Terminology</h3>
+
+ <p>This document uses the following terms as defined in JSON [[!RFC4627]]. Refer
+ to the <em>JSON Grammar</em> section in [[!RFC4627]] for formal definitions.</p>
+
+ <dl>
+ <dt><tdef>JSON object</tdef></dt>
+ <dd>An object structure is represented as a pair of curly brackets
+ surrounding zero or more key-value pairs. A key is a
+ <tref>string</tref>. A single colon comes after each key, separating the
+ key from the value. A single comma separates a value from a following
+ key.</dd>
+ <dt><tdef>array</tdef></dt>
+ <dd>An array structure is represented as square brackets surrounding zero
+ or more values (or elements). Elements are separated by commas.
+ In JSON, an array is an <em>ordered</em> sequence of zero or more values.
+ While JSON-LD uses the same array representation as JSON,
+ the collection is <em>unordered</em> by default. While order is
+ preserved in regular JSON arrays, it is not in regular JSON-LD arrays
+ unless specific markup is provided (see <a href="#sets-and-lists"></a>).</dd>
+ <dt><tdef>string</tdef></dt>
+ <dd>A string is a sequence of zero or more Unicode characters,
+ wrapped in double quotes, using backslash escapes (if necessary). A
+ character is represented as a single character string.</dd>
+ <dt><tdef>number</tdef></dt>
+ <dd>A number 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><tdef>true</tdef> and <tdef>false</tdef></dt>
+ <dd>Values that are used to express one of two possible boolean states.</dd>
+ <dt><tdef>null</tdef></dt>
+ <dd>The <tref>null</tref> value. A key-value pair in the
+ <code>@context</code> where the value, or the <code>@id</code> of the
+ value, is <tref>null</tref> explicitly decouples a term's association
+ with an IRI. A key-value pair in the body of a JSON-LD document whose
+ value is <tref>null</tref> has the same meaning as if the key-value pair
+ was not defined. If <code>@value</code>, <code>@list</code>, or
+ <code>@set</code> is set to <tref>null</tref> in expanded form, then
+ the entire <tref>JSON object</tref> is ignored.</dd>
+ </dl>
+
+ <p>Furthermore, the following terminology is used throughout this document:</p>
+
+ <dl>
+ <dt><tdef>keyword</tdef></dt>
+ <dd>A JSON key that is specific to JSON-LD, specified in the JSON-LD Syntax specification [[!JSON-LD]]
+ in the section titled <cite><a href="../json-ld-syntax/#syntax-tokens-and-keywords">Syntax Tokens and Keywords</a></cite>.</dd>
+ <dt><tdef>context</tdef></dt>
+ <dd>A a set of rules for interpreting a JSON-LD document as specified in
+ <cite><a href="../json-ld-syntax/#the-context">The Context</a></cite> of the [[JSON-LD]] specification.</dd>
+ <dt><tdef>JSON-LD document</tdef></dt>
+ <dd>A <tref>JSON-LD document</tref> is a serialization of a collection of
+ <tref title="JSON-LD graph">JSON-LD graphs</tref> and comprises exactly one
+ <tref>default graph</tref> and zero or more <tref title="named graph">named graphs</tref>.</dd>
+ <dt><tdef>named graph</tdef></dt>
+ <dd>A named graph is a pair consisting of an <tref>IRI</tref> or <tref>blank node</tref>
+ (the <tdef>graph name</tdef>) and a <tref>JSON-LD graph</tref>.</dd>
+ <dt><tdef>default graph</tdef></dt>
+ <dd>The default graph is the only graph in a JSON-LD document which has no <tref>graph name</tref>.</dd>
+ <dt><tdef>JSON-LD graph</tdef></dt>
+ <dd>A labeled directed graph, i.e., a set of <tref title="node">nodes</tref> connected by <tref title="edge">edges</tref>,
+ as specified in the <cite><a href="../json-ld-syntax/#data-model">Data Model</a></cite> section of the JSON-LD syntax
+ specification [[!JSON-LD]].</dd>
+ <dt><tdef>edge</tdef></dt>
+ <dd>Every <tref>edge</tref> has a direction associated with it and is labeled with
+ an <tref>IRI</tref> or a <tref>blank node identifier</tref>. Within the JSON-LD syntax
+ these edge labels are called <tdef title="property">properties</tdef>. Whenever possible, an
+ <tref>edge</tref> SHOULD be labeled with an <tref>IRI</tref>.</dd>
+ <dt><tdef>node</tdef></dt>
+ <dd>Every <tref>node</tref> is an <tref>IRI</tref>, a <tref>blank node</tref>,
+ a <tref>JSON-LD value</tref>, or a <tref>list</tref>.</dd>
+ <dt><tdef><abbr title="Internationalized Resource Identifier">IRI</abbr></tdef></dt>
+ <dd>An <tref>IRI</tref> (Internationalized Resource Identifier) is a string that conforms to the syntax
+ defined in [[RFC3987]].</dd>
+ <dt><tdef>absolute IRI</tdef></dt>
+ <dd>An absolute IRI is defined in [[!RFC3987]] containing a <em>scheme</em> along with a <em>path</em> and
+ optional <em>query</em> and fragment segments.</dd>
+ <dt><tdef>relative IRI</tdef></dt>
+ <dd>A relative IRI is an IRI that is relative some other <tref>absolute IRI</tref>;
+ in the case of JSON-LD this is the base location of the document.</dd>
+ <dt><tdef>blank node</tdef></dt>
+ <dd>A <tref>node</tref> in a <tref>JSON-LD graph</tref> that does not contain a de-referenceable
+ identifier because it is either ephemeral in nature or does not contain information that needs to be
+ linked to from outside of the JSON-LD graph.</dd>
+ <dt><tdef>blank node identifier</tdef></dt>
+ <dd>A blank node identifier is a string that can be used as an identifier for a <tref>blank node</tref> within
+ the scope of a JSON-LD document. Blank node identifiers begin with <code>_:</code>.</dd>
+ <dt><tdef>JSON-LD value</tdef></dt>
+ <dd>A <tref>JSON-LD value</tref> is a <tref>string</tref>, a <tref>number</tref>,
+ <tref>true</tref> or <tref>false</tref>, a <tref>typed value</tref>, or a
+ <tref>language-tagged string</tref>.</dd>
+ <dt><tdef>typed value</tdef></dt>
+ <dd>A <tref>typed value</tref> consists of a value, which is a string, and a type, which is an <tref>IRI</tref>.</dd>
+ <dt><tdef>language-tagged string</tdef></dt>
+ <dd>A <tref>language-tagged string</tref> consists of a string and a non-empty language
+ tag as defined by [[BCP47]]. The language tag must be well-formed according to section
+ <a href="http://tools.ietf.org/html/bcp47#section-2.2.9">2.2.9</a> of [[BCP47]], and MUST
+ be normalized to lowercase.</dd>
+ <dt><tdef>list</tdef></dt>
+ <dd>A <tref>list</tref> is an ordered sequence of <tref title="IRI">IRIs</tref>,
+ <tref title="blank node">blank nodes</tref>, and
+ <tref title="JSON-LD value">JSON-LD values</tref>.</dd>
+ </dl>
+</section>
+
+<section>
+<h1>Algorithms</h1>
+
+<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 MUST be used where applicable.</p>
+
+<section>
+ <h2>Algorithm Terms</h2>
+ <dl>
+ <dt><tdef>active graph</tdef></dt>
+ <dd>The name of the currently active graph that the processor should use when
+ processing.</dd>
+ <dt><tdef>active subject</tdef></dt>
+ <dd>The currently active subject that the processor should use when
+ processing.</dd>
+ <dt><tdef>active property</tdef></dt>
+ <dd>The currently active property that the processor should use when
+ processing. The active property is represented in the original lexical form, which
+ is used for finding type mappings in the <tref>active context</tref>.</dd>
+ <dt><tdef>active object</tdef></dt>
+ <dd>The currently active object that the processor should use when
+ processing.</dd>
+ <dt><tdef>active context</tdef></dt>
+ <dd>A context that is used to resolve <tref>term</tref>s while the processing
+ algorithm is running. The <tref>active context</tref> is the context
+ contained within the <tref>processor state</tref>.</dd>
+ <dt><tdef>local context</tdef></dt>
+ <dd>A context that is specified within a <tref>JSON object</tref>,
+ specified via the <code>@context</code> <tref>keyword</tref>.</dd>
+ <dt><tdef>processor state</tdef></dt>
+ <dd>The <tref>processor state</tref>, which includes the <tref>active
+ context</tref>, <tref>active subject</tref>, and
+ <tref>active property</tref>. The <tref>processor state</tref> is managed
+ as a stack with elements from the previous <tref>processor state</tref>
+ copied into a new <tref>processor state</tref> when entering a new
+ <tref>JSON object</tref>.</dd>
+ <dt><tdef>JSON-LD input</tdef></dt>
+ <dd>The JSON-LD data structure that is provided as input to the algorithm.</dd>
+ <dt><tdef>JSON-LD output</tdef></dt>
+ <dd>The JSON-LD data structure that is produced as output by the algorithm.</dd>
+ <dt><tdef>term</tdef></dt>
+ <dd>A <tref>term</tref> is a short word defined in a context that MAY be expanded to an <tref>IRI</tref></dd>
+ <dt><tdef>compact IRI</tdef></dt>
+ <dd>A compact IRI is has the form of <tdef>prefix</tdef>:<em>suffix</em> and is used as a way
+ of expressing an IRI without needing to define separate <tref>term</tref> definitions for
+ each IRI contained within a common vocabulary identified by <tref>prefix</tref>.</dd>
+ <dt><tdef>node object</tdef></dt>
+ <dd>A <tref>node object</tref> represents zero or more properties of a
+ <tref>node</tref> in the <tref>JSON-LD graph</tref> serialized by the
+ JSON-LD document. A <tref>JSON object</tref> is a <tref>node object</tref>
+ if it exists outside of the JSON-LD <tref>context</tref> and:
+ <ul>
+ <li>it does not contain the <code>@value</code>, <code>@list</code>,
+ or <code>@set</code> keywords, or</li>
+ <li>it is not the top-level <tref>JSON object</tref> in the JSON-LD document containing
+ the <code>@graph</code> keyword.</li>
+ </ul>
+ </dd>
+ <dt><tdef>list object</tdef></dt>
+ <dd>A <tref>list object</tref> is a <tref>JSON object</tref> that has a <code>@list</code>
+ member.</dd>
+ <dt><tdef>scalar</tdef></dt>
+ <dd>A scalar is either a JSON <tref>string</tref>, <tref>number</tref>, <tref>true</tref>,
+ or <tref>false</tref>.</dd>
+ <dt><tdef>quad</tdef></dt>
+ <dd>An <em>RDF triple</em> as specified by [[RDF-CONCEPTS]] augmented with a a fourth component,
+ a <tref>graph name</tref>.</dd>
+ </dl>
+</section>
+
+<section>
+ <h2>Expansion Algorithm</h2>
+
+ <p>The algorithm takes three input variables: an <tref>active context</tref>,
+ an <tref>active property</tref>, and an <em>element</em> to be expanded. To
+ begin, the <tref>active context</tref> is set to the result of performing, <a
+ href="#context-processing">Context Processing</a> on the passed
+ <code class="idlMemberName"><a href="#widl-JsonLdOptions-expandContext">expandContext</a></code>,
+ or empty if <code class="idlMemberName"><a href="#widl-JsonLdOptions-expandContext">expandContext</a></code>
+ is <tref>null</tref>, <tref>active property</tref> is set to <tref>null</tref>, and
+ <em>element</em> is set to the <tref>JSON-LD input</tref>. This algorithm expects the
+ <tref>JSON-LD input</tref> to be a well-formed JSON-LD document as defined in [[!JSON-LD]].</p>
+
+ <ol class="algorithm">
+ <li>If <em>element</em> is a <tref>scalar</tref>, expand it according to the
+ <a href="#value-expansion">Value Expansion</a> algorithm, passing copies of the
+ <tref>active context</tref> and <tref>active property</tref> and return.</li>
+ <li>If <em>element</em> is <tref>null</tref>, return.</li>
+ <li>If <em>element</em> is an <tref>array</tref>,
+ <ol class="algorithm">
+ <li>initialize an empty array <em>result</em>.</li>
+ <li>Expand each <em>item</em> by recursively using this algorithm, passing copies of
+ the <tref>active context</tref> and <tref>active property</tref>.</li>
+ <li>If the <tref title="active property">active property's</tref>
+ <tref>container mapping</tref> is set to <code>@list</code>, the expanded
+ <em>item</em> MUST NOT be an <tref>array</tref> or a <tref>list object</tref>.</li>
+ <li>If the expanded <em>item</em> is <tref>null</tref>, drop it.</li>
+ <li>Otherwise, if the expanded <em>item</em> is an <tref>array</tref>, merge its
+ entries with <em>result's</em> entries.</li>
+ <li>Otherwise, append <em>item</em> to <em>result</em>.</li>
+ <li>Finally, set <em>element</em> to <em>result</em> and return.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>element</em> MUST be an object
+ <ol class="algorithm">
+ <li>If <em>element</em> has a <code>@context</code> member, update the
+ <tref>active context</tref> according to the steps outlined in
+ <a href="#context-processing">Context Processing</a> and remove the
+ <code>@context</code> member.</li>
+ <li>Initialize an empty <tref>JSON object</tref> <em>result</em>.</li>
+
+ <li>Process each <em>property</em> and <em>value</em> in <em>element</em>
+ ordered by <em>property</em> as follows:
+ <ol class="algorithm">
+
+ <li>For each <tref>property generator</tref> <em>pg</em> in the <tref>active context</tref>
+ ordered lexically by term name:
+ <ol class="algorithm">
+ <li>Remove <em>property</em> from <em>element</em>, expand
+ <em>property</em> according to the steps outlined in <a href="#iri-expansion">IRI Expansion</a>
+ as <em>expanded property</em> passing <code>true</code> for <em>vocabRelative</em> and <em>relableBlankNodes</em> flags.
+ Set the <tref>active property</tref> to the original un-expanded <em>property</em> if
+ <em>property</em> is not a <tref>keyword</tref>.</li>
+ <li>If <em>expanded property</em> is an <tref>array</tref>, remove every element which is not a
+ <tref>absolute IRI</tref>.</li>
+ <li>If <em>expanded property</em> is an empty array, or <code>null</code>,
+ continue with the next property from <em>element</em>.
+ <li>If <em>expanded property</em> is a <tref>keyword</tref>, process it as
+ follows:
+ <ol class="algorithm">
+ <li>If <em>expanded property</em> is <code>@id</code>, <em>value</em> MUST be a <tref>string</tref>.
+ Set the <code>@id</code>
+ member of <em>result</em> to the result of expanding <em>value</em>
+ according the <a href="#iri-expansion">IRI Expansion algorithm</a> (passing <code>true</code>
+ for the <em>documentRelative</em> and <em>relabelBlankNodes</em> flags).</li>
+ <li>If <em>expanded property</em> is <code>@type</code>, <em>value</em> MUST be a <tref>string</tref>
+ or <tref>array</tref> of <tref title="string">strings</tref>. Set the <code>@type</code>
+ member of <em>result</em> to the result of expanding <em>value</em>
+ according the <a href="#iri-expansion">IRI Expansion algorithm</a> (passing <code>true</code>
+ for both the <em>documentRelative</em>, <em>vocabRelative</em>, and <em>relabelBlankNodes</em> flags).
+ Empty <tref title="array">arrays</tref> are ignored.</li>
+ <li>If <em>expanded property</em> is <code>@value</code>, <em>value</em> MUST be a <tref>scalar</tref>
+ or <tref>null</tref>. Set the <code>@value</code>
+ member of <em>result</em> to <em>value</em>.</li>
+ <li>If <em>expanded property</em> is <code>@language</code>, <em>value</em> MUST be a <tref>string</tref>
+ or <tref>null</tref>.
+ Set the <code>@language</code> member of <em>result</em> to the lowercased <em>value</em>.</li>
+ <li>If <em>expanded property</em> is <code>@annotation</code> <em>value</em> MUST be a <tref>string</tref>.
+ Set the <code>@annotation</code> member of <em>result</em> to <em>value</em>.</li>
+ <li>If <em>expanded property</em> is <code>@set</code> or <code>@list</code>, set the
+ <em>expanded property</em> member of <em>result</em> to the result of expanding <em>value</em> by
+ recursively using this algorithm, passing copies of the <tref>active context</tref> and
+ <tref>active property</tref>.</li>
+ <li>If <em>expanded property</em> id <code>@graph</code>, set the <code>@graph</code>
+ member of <em>result</em> to the result of expanding <em>value</em> by
+ recursively using this algorithm, passing copies of the <tref>active context</tref> and
+ <code>@graph</code> as <tref>active property</tref>.</li>
+ <li>Continue with the next <em>property</em>-<em>value</em> pair from <em>element</em>.</li>
+ </ol>
+ </li>
+ <li>If <em>expanded property</em> is neither a <tref>blank node identifier</tref> nor an
+ <tref>absolute IRI</tref>,i.e., it is <tref>null</tref> or does not contain a colon
+ (<code>:</code>), continue with the next member from <em>element</em>.</li>
+ <li>Otherwise, if <em>property's</em> <tref>container mapping</tref> is set to
+ <code>@language</code>
+ <ol class="algorithm">
+ <li>Initialize a new empty <tref>array</tref> <em>language map values</em>.</li>
+ <li>Process each <em>key</em>-<em>val</em> pair of <em>value</em> ordered by
+ <em>key</em> as follows:
+ <ol class="algorithm">
+ <li>If <em>val</em> is not an array, transform it to one.</li>
+ <li>For each item of <em>val</em>, construct a new <tref>JSON object</tref>
+ consisting of two members: <code>@value</code> set to the currently
+ processed item, which MUST be a <tref>string</tref>, and <code>@language</code> set to the lowercased <em>key</em>.
+ Append the object to <em>language map values</em>.</li>
+ </ol>
+ </li>
+ <li>Set <em>value</em> to <em>language map values</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>property's</em> <tref>container mapping</tref> is set to
+ <code>@annotation</code>
+ <ol class="algorithm">
+ <li>Initialize a new empty <tref>array</tref> <em>annotation map values</em>.</li>
+ <li>Process each <em>key</em>-<em>val</em> pair of <em>value</em> ordered by
+ <em>key</em> as follows:
+ <ol class="algorithm">
+ <li>If <em>val</em> is not an array, transform it to one.</li>
+ <li>Expand <em>val</em> by recursively using this algorithm, passing copies of
+ the <tref>active context</tref> and <tref>active property</tref>.</li>
+ <li>Add to each item of <em>val</em> a member <code>@annotation</code> set to
+ <em>key</em> if no such member exists and append the resulting
+ <tref>JSON object</tref> to <em>annotation map values</em>.</li>
+ </ol>
+ </li>
+ <li>Set <em>value</em> to <em>annotation map values</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, expand <em>value</em> by recursively using this algorithm, passing
+ copies of the <tref>active context</tref> and <em>property</em> as
+ <tref>active property</tref>.</li>
+ <li>If the expanded <em>value</em> is <tref>null</tref>, continue with the next
+ <em>property</em>-<em>value</em> pair from <em>element</em>.</li>
+ <li>If <em>property's</em> <tref>container mapping</tref> is set to <code>@list</code> and
+ <em>value</em> is either not an <tref>JSON object</tref> or a <tref>JSON object</tref>
+ without an <code>@list</code> member, replace <em>value</em> with a
+ <tref>JSON object</tref> with an <code>@list</code> member whose value is set to
+ <em>value</em> (wrapped in an <tref>array</tref> if it is not already one).</li>
+ <li>If <em>expanded property</em> is an <tref>array</tref>,
+ <ol class="algorithm">
+ <li>label all <tref title="blank node">blank nodes</tref> in <em>value</em> with
+ <tref title="blank node identifier">blank node identifiers</tref> by using the
+ <a href="#label-blank-nodes-algorithm">Label Blank Nodes Algorithm</a>.</li>
+ <li>Then, for each <em>iri</em> of <em>expanded property</em> merge a copy
+ of <em>value</em> into the <em>iri</em> member of the <em>result</em>
+ <tref>JSON object</tref> as an <tref>array</tref> member.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set <em>element</em> to <em>result</em>.</li>
+ <li>If the processed <em>element</em> has an <code>@value</code> property
+ <ol class="algorithm">
+ <li>Remove any <code>@type</code> or <code>@language</code> members with <tref>null</tref> or empty values.</tref>
+ <li>Other than <code>@annotation</code>, <em>element</em> MUST NOT have more than one other member,
+ which can either be <code>@language</code> or <code>@type</code> with a <tref>string</tref> value.</li>
+ <li>If the value of <code>@value</code> is <tref>null</tref>, replace <em>element</em> with <tref>null</tref>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>element</em> has an <code>@type</code> member and its value is not in the form of an
+ <tref>array</tref>, convert it to an <tref>array</tref>.</li>
+ <li>If <em>element</em> has an <code>@set</code> or <code>@list</code> member, it MUST be the only member other than
+ <code>@annotation</code>.
+ Set <em>element</em> to the value of <code>@set</code>; leave <code>@list</code> untouched.</li>
+ <li>If <em>element</em> has just a <code>@language</code> property, set <em>element</em> to <tref>null</tref>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>If, after the algorithm outlined above is run, the resulting <em>element</em> is an
+ <tref>JSON object</tref> with just a <code>@graph</code> member, <em>element</em> is set to
+ the value of <code>@graph</code>'s value. Finally, if <em>element</em> is a <tref>JSON object</tref>,
+ it is wrapped into an <tref>array</tref>.</p>
+
+ <p>If the <code class="idlMemberName"><a href="#widl-JsonLdOptions-flatten">flatten</a></code> option is not <code>false</code>, run the
+ <a href="#flattening-algorithm">Flattening Algorithm</a>.</p>
+</section>
+
+<section>
+ <h2 id="context">Context Processing</h2>
+ <p>Processing of JSON-LD data structure is managed recursively.
+ During processing, each rule is applied using information provided by the <tref>active context</tref>.</p>
+
+ <p>Processing begins by pushing a new <tref>processor state</tref> onto the <tref>processor state</tref> stack.
+ If a <tref>local context</tref> is encountered, information from the <tref>local context</tref> is merged
+ into the <tref>active context</tref>.</p>
+
+ <p>The <tref>active context</tref> contains the active <tdef title="term definition">term definitions</tdef>
+ which specify how properties and values have to be interpreted as well as the current
+ <tdef>vocabulary mapping</tdef> and the <tdef>default language</tdef>. Each <tref>term definition</tref> consists
+ of an <tdef>IRI mapping</tdef> and optionally a <tdef>type mapping</tdef> from terms to datatypes or
+ <tdef>language mapping</tdef> from terms to language codes, and a <tdef>container mapping</tdef>. If an
+ <tref>IRI mapping</tref> maps a term to multiple <tref="IRI">IRIs</tref> it is said to be a
+ <tdef>property generator</tdef>.</p>
+
+ <p>A <tref>local context</tref> is identified within a <tref>JSON object</tref> having a <code>@context</code>
+ property with a <tref>string</tref>, <tref>array</tref> or a <tref>JSON object</tref> value.
+ When processing a <tref>local context</tref>, special processing rules apply:</p>
+
+ <p>All calls of the <a href="#iri-expansion">IRI Expansion algorithm</a> pass the value specified in the
+ algorithm along with the <tref>local context</tref> and <code>true</code> for the <em>vocabRelative</em> flag.</p>
+
+ <ol class="algorithm">
+ <li>Initialize <tref>local context</tref> with a copy of any passed <tref>active context</tref>, or to an empty
+ <tref>JSON object</tref> otherwise.</li>
+ <li>Let <em>context</em> be the value of <code>@context</code>
+ <ol class="algorithm">
+ <li id="process-context">If <em>context</em> equals <tref>null</tref>, clear <tref>local context</tref>.</li>
+ <li>If <em>context</em> is an <tref>array</tref>, process each element as <em>context</em> in order
+ recursively using this algorithm using the <tref>local context</tref>.</li>
+ <li>If <em>context</em> is a <tref>string</tref>, it MUST have a lexical form of <tref>IRI</tref>.
+ <ol class="algorithm">
+ <li>Expand <em>context</em> according to <a href="#iri-expansion">IRI Expansion</a>
+ using the <tref>local context</tref> relative to the enclosing document.
+ Processors MUST NOT process a previously processed <em>context</em>.</li>
+ <li>Dereference <em>context</em>.</li>
+ <li>The resulting document MUST be a JSON document; extract the value of any <code>@context</code>
+ key and process it's value recursively using this algorithm using the <tref>local context</tref>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, <em>context</em> MUST be a <tref>JSON object</tref>, perform the following steps:
+ <ol class="algorithm">
+ <li>If the <tref>local context</tref> does not have a <tref>vocabulary mapping</tref>, initialize
+ it to the document base.</tref>
+ <li>If <em>context</em> has a <code>@vocab</code> member, it MUST have a value of a
+ simple <tref>string</tref> with the lexical form described in [[!BCP47]], or <tref>null</tref>.
+ Set the <tref title="active context">local context's</tref>
+ <tref>vocabulary mapping</tref> to its value and remove the <code>@vocab</code>
+ member from <em>context</em>.</li>
+ <li>If <em>context</em> has a <code>@language</code> member it MUST have a value of a
+ simple <tref>string</tref> with the lexical form described in [[!BCP47]], or <tref>null</tref>.
+ Set the
+ <tref title="active context">local context's</tref> <tref>default language</tref> to
+ its value and remove the <code>@language</code> member from <em>context</em>.</li>
+ <li>For each other <em>key</em>-<em>value</em> pair in <em>context</em> perform the
+ following steps:
+ <ol class="algorithm">
+ <li>Remove the <em>key</em>-<em>value</em> pair from <em>context</em>.
+ <span class="issue">We have lost the iterative nature of this algorithm, which allows for
+ multiple passes to resolve prefix dependencies, and the ability to detect cycles.</span></li>
+ <li>If <em>key</em> is a JSON-LD <tref>keyword</tref>, continue with the next
+ <em>key</em>-<em>value</em> pair.</li>
+ <li>If <em>value</em> is <tref>null</tref>, replace the <tref>term definition</tref>
+ for <em>key</em> in the <tref>active context</tref> with an <tref>IRI mapping</tref>
+ set to <tref>null</tref> and continue with the next <em>key</em>-<em>value</em> pair.</li>
+ <li>If <em>value</em> is a <tref>string</tref>, expand it according to the
+ <a href="#iri-expansion">IRI Expansion algorithm</a> using the <tref>local context</tref>
+ relative to the <tref>vocabulary mapping</tref> and replace the
+ <tref>term definition</tref> for <em>key</em> in the <tref>local context</tref> with
+ an <tref>IRI mapping</tref> set to the expanded <em>value</em>. Continue with
+ the next <em>key</em>-<em>value</em> pair.</li>
+ <li>Otherwise, <em>value</em> MUST be a <tref>JSON object</tref>.
+ If <tref>term definition</tref> for <em>key</em> exists in
+ the <tref>active context</tref>, remove it.</li>
+ <li>Initialize a new, empty <tref>term definition</tref> <em>definition</em>.</li>
+ <li>If <em>value</em> has an <code>@id</code> member with a value <em>val</em>:
+ <ol class="algorithm">
+ <li>if <em>val</em> is an <tref>array</tref>, each <em>item</em> in <em>val</em>
+ MUST be a <tref>string</tref>:
+ <ol class="algorithm">
+ <li>expand each <em>item</em> in the array according the
+ <a href="#iri-expansion">IRI Expansion algorithm</a>;
+ <em>item</em> MUST expand to an <tref>absolute IRI</tref> or
+ <tref>blank node identifier</tref>.</li>
+ <li>Lexicographically sort <em>val</em> and set the <tref>IRI mapping</tref>
+ of <em>definition</em> to <em>val</em>.</li>
+ </ol>
+ <li>Otherwise, expand <em>val</em> according the
+ <a href="#iri-expansion">IRI Expansion algorithm</a> and set the
+ <tref>IRI mapping</tref> of <em>definition</em> to <em>val</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, set the <tref>IRI mapping</tref> of <em>definition</em> to the result of
+ expanding <em>key</em> according the <a href="#iri-expansion">IRI Expansion algorithm</a>.</li>
+ <li>If the <tref>IRI mapping</tref> of <em>definition</em> is set to <tref>null</tref> or a
+ <tref>keyword</tref>, store <em>definition</em> as the <tref>term definition</tref>
+ for <em>key</em> in the <tref>local context</tref> and continue with the next
+ <em>key</em>-<em>value</em> pair from <em>context</em>.</li>
+ <li>Otherwise, if <tref>IRI mapping</tref> of <em>definition</em> MUST be
+ a <tref>string</tref> with the lexical representation of <tref>absolute IRI</tref>.</li>
+ <li>If <em>value</em> has an <code>@type</code> member with a value <em>val</em>,
+ <em>val</em> MUST expand to an <tref>absolute IRI</tref> using the
+ <a href="#iri-expansion">IRI Expansion algorithm</a>. Set the
+ <tref>type mapping</tref> of <em>definition</em> to the expanded <em>val</em>.</li>
+ <li>Otherwise, if <em>value</em> has an <code>@language</code> member with a value <em>val</em>,
+ <em>val</em> MUST be a <tref>string</tref> having the lexical representation defined in [[!BCP47]]
+ or <tref>null</tref>, set the <tref>language mapping</tref> of
+ <em>definition</em> to the lowercased <em>val</em>.</li>
+ <li>If <em>value</em> has an <code>@container</code> member with a value <em>val</em>
+ it MUST be one of <code>@list</code>, <code>@set</code>, or <code>@annotation</code>, set the
+ <tref>container mapping</tref> of <em>definition</em> to <em>val</em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+
+</section>
+
+<section>
+ <h2>IRI Expansion</h2>
+ <p>Keys and some values are evaluated to produce an <tref>IRI</tref>. This section defines an algorithm for
+ transforming a value representing an IRI into an <tref>absolute IRI</tref>. If <tref>IRI</tref> expansion
+ occurs during context processing, the <tref>local context</tref> that is being processed
+ is passed to this algorithm. After application of this algorithm, values processed by this
+ algorithm are said to be in <tdef>expanded IRI form</tdef>, although this may also include
+ named <tref title="blank node">blank nodes</tref>.</p>
+
+ <p>The algorithm takes two mandatory and three optional input variables: a <em>value</em>
+ to be expanded, an <tref>active context</tref>, three flags <em>documentRelative</em>,
+ <em>vocabRelative</em> specifying whether <em>value</em> should be interpreted as
+ <tref>relative IRI</tref> against the document's base IRI or the
+ <tref title="active context">active context's</tref> <tref>vocabulary mapping</tref>,
+ and <em>relabelBlankNodes</em> indicating that values expanding to a <tref>blank node identifier</tref>
+ are to be re-labeled.</p>
+
+ <p>The algorithm for generating an IRI is:</p>
+
+ <ol class="algorithm">
+ <li>If a <tref>local context</tref> is being processed and the value is in the
+ <tref>local context</tref> but the value's processing state is not <em>finished</em>, then
+ process the value using <a href="#context-process-property">step 2.4.3.1</a> of the
+ <a href="#context">Context Processing algorithm</a>.</li>
+ <li>If the <tref>active context</tref> contains a <tref>term</tref> mapping for the value using
+ a case-sensitive comparison, use the mapped value, unless a <tref>local context</tref>
+ is being processed, in which case, return the result of recursing to expand the mapped value.</li>
+ <li>Otherwise, 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 value represents a named <tref>blank node</tref>.</li>
+ <li>If a <tref>local context</tref> is being processed and the <em>prefix</em> is in the
+ <tref>local context</tref> but it's processing state is not <em>finished</em>, then
+ process the <em>prefix</em> using <a href="#context-process-property">step 2.4.3.1</a> of the
+ <a href="#context">Context Processing algorithm</a>.</li>
+ <li>If the <tref>active context</tref> contains a <tref>term</tref> mapping for <em>prefix</em> using
+ a case-sensitive comparison, and <em>suffix</em> does not does not begin with '//'
+ (i.e., it does not match a <em>hier-part</em> including
+ <em>authority</em> (as defined in [[!RFC3986]]), generate an <tref>IRI</tref>
+ 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>Otherwise, if the <em>vocabRelative</em> flag is set to <code>true</code> and the
+ <tref>active context</tref> contains a <tref>vocabulary mapping</tref>, generate and return an
+ <tref>IRI</tref> by prepending the <tref>IRI</tref> of the <tref>vocabulary mapping</tref>
+ to the <em>value</em> using textual concatenation.</li>
+ <li>Otherwise, if the <em>documentRelative</em> flag is set to <code>true</code>, resolve <em>value</em>
+ against the base IRI as per [[!RFC3986]] and return the resulting <tref>IRI</tref>. Only the basic
+ algorithm in section 5.2 of [[!RFC3986]] is used; neither <em>Syntax-Based Normalization</em>
+ nor <em>Scheme-Based Normalization</em> (as described in sections 6.2.2 and 6.2.3 of [[!RFC3986]])
+ are performed. Characters additionally allowed in IRI references are treated in the same way that
+ unreserved characters are treated in URI references, per section 6.5 of [[!RFC3987]]</li>
+ <li>Otherwise return <em>value</em> as is.</li>
+ </ol>
+
+ <p>If the <em>relabelBlankNodes</em> flag ist set, and the result of the algorithm above is a <tref>blank node identifier</tref>,
+ <a href="#generate-blank-node-identifier">generated a new blank node identifier</a> before returning the
+ final result.</p>
+</section>
+
+<section>
+ <h2>Value Expansion</h2>
+
+ <p>Some values in JSON-LD can be expressed in a <tref>compacted form</tref>. These values
+ are required to be expanded at times when processing JSON-LD documents.
+ A value is said to be in <tdef>expanded form</tdef> after
+ the application of this algorithm.</p>
+
+ <p>The algorithm for expanding a <em>value</em> takes an <tref>active property</tref>
+ and <tref>active context</tref>. It is implemented as follows:</p>
+
+ <ol class="algorithm">
+ <li>If <em>value</em> is <tref>null</tref>, return <tref>null</tref>.</li>
+ <li>Initialize an empty object <em>result</em>.</li>
+ <li>If <tref>active property</tref> is <code>@graph</code> or the
+ <tref title="active property">active property's</tref> <tref>type mapping</tref> is set to
+ <code>@id</code>, add a key-value pair to <em>result</em> where the key is <code>@id</code>
+ and the value is the result of expanding <em>value</em> according to the
+ <a href="#iri-expansion">IRI Expansion algorithm</a> passing <code>true</code> for the
+ <em>documentRelative</em> flag. Then return <em>result</em>.</li>
+ <li>Add a key-value pair to <em>result</em> where the key is <code>@value</code>
+ and the value is <em>value</em>.</li>
+ <li>If the <tref>active property</tref> has a <tref>type mapping</tref>, add a key-value
+ pair to <em>result</em> where the key is <code>@type</code> and the value is the
+ <tref>IRI</tref> associated with the <tref>type mapping</tref> or a newly
+ <a href="#generate-blank-node-identifier">generated blank node identifier</a> if the
+ <tref>type mapping</tref> is set to a <tref>blank node identifier</tref>.</li>
+ <li>Otherwise, if <em>value</em> is a <tref>string</tref> and the <tref>active property</tref> has a
+ <tref>language mapping</tref> or an <tref>default language</tref> is set in the <tref>active context</tref>,
+ add a key-value pair to <em>result</em> where the key is <code>@language</code> and the value is the
+ language tag associated with the <tref>language mapping</tref> or the <tref>active property</tref> or the
+ <tref>default language</tref>.</li>
+ <li>Return <em>result</em>.</li>
+ </ol>
+</section>
+
+<section>
+ <h2>Label Blank Nodes Algorithm</h2>
+
+ <p>The algorithm takes a single input variable: an <em>element</em> to be labeled with
+ <tref title="blank node identifier">blank node identifiers</tref>.</p>
+
+ <ol class="algorithm">
+ <li>If <em>element</em> is an <tref>array</tref>, recursively apply this
+ algorithm to all its items.</li>
+ <li>Otherwise, if <em>element</em> is a <tref>JSON object</tref> with a
+ <code>@list</code> member, recursively apply this algorithm to all items
+ of the <code>@list</code> member's value.</li>
+ <li>Otherwise, if <em>element</em> is a <tref>JSON object</tref>
+ <ol class="algorithm">
+ <li>For each <em>key</em>-<em>value</em> pair ordered by <em>key</em>
+ recursively apply this algorithm to <em>value</em>.</li>
+ <li>If <em>element</em> is a <tref>node object</tref> without an <code>@id</code> member,
+ create a new <code>@id</code> member and assign it a new
+ <tref>blank node identifier</tref> according the
+ <a href="#generate-blank-node-identifier">Generate Blank Node Identifier</a> algorithm.</li>
+ </ol>
+ </li>
+ </ol>
+</section>
+
+<section>
+ <h2>Generate Blank Node Identifier</h2>
+
+ <p>This algorithm is used to generate new
+ <tref title="blank node identifier">blank node identifiers</tref> or to relabel existing
+ <tref title="blank node identifier">blank node identifiers</tref> with a new one to avoid
+ collision by the introduction of new ones. It needs to keep an <em>identifier map</em>,
+ a <em>counter</em>, and a <em>prefix</em> between its executions to be able to generate new
+ <tref title="blank node identifier">blank node identifiers</tref>. The <em>counter</em>
+ is initialized to <code>0</code> and <em>prefix</em> is set to <code>_:t</code> by default.</p>
+
+ <p>The algorithm takes a single input variable <em>identifier</em> which might be
+ <tref>null</tref>.</p>
+
+ <ol class="algorithm">
+ <li>If the <em>identifier</em> is not <tref>null</tref> and is in the <em>identifier map</em>,
+ return the mapped identifier.</li>
+ <li>Otherwise, generate a new <em>blankNodeIdentifier</em> by concatenating <em>prefix</em>
+ and <em>counter</em>.</li>
+ <li>Increment <em>counter</em> by <code>1</code>.</li>
+ <li>If <em>identifier</em> is not <tref>null</tref>, create a new entry in
+ <em>identifier map</em> set to <em>blankNodeIdentifer</em>.</li>
+ <li>Return <em>blankNodeIdentifier</em>.</li>
+ </ol>
+</section>
+
+<section>
+ <h3>IRI Compaction Algorithm</h3>
+
+ <p>This section defines an algorithm for transforming an <tref>IRI</tref> to a
+ <tref>term</tref> or <tref>compact IRI</tref> using an <tref>active context</tref>.
+ If a <em>value</em> is passed it is used to choose the best matching <tref>term</tref>.</p>
+
+ <p>The algorithm for generating a <tref>compact IRI</tref> is:
+ <ol class="algorithm">
+ <li>Create an empty list of terms <em>terms</em> that will be populated with
+ <tref>term</tref>s that are ranked according to how closely they match
+ <em>value</em>. Initialize <em>highest rank</em> to <code>0</code>,
+ and set a flag <em>list container</em> to <code>false</code>.</li>
+ <li>For each <em>term</em> in the <tref>active context</tref>:
+ <ol class="algorithm">
+ <li>If the <em>term</em>'s <tref>IRI</tref> is not a complete match against
+ <em>iri</em>, continue to the next <em>term</em>.</li>
+ <li>If <em>value</em> is a <tref>JSON object</tref> containing only the property <code>@list</code>
+ and not containing the property <code>@annotation</code>:
+ <ol class="algorithm">
+ <li>If <em>term</em> has a <code>@container</code> set to <code>@set</code>, continue
+ to the next <em>term</em>.</li>
+ <li>If <em>list container</em> is <code>true</code> and <em>term</em> does not have a
+ <code>@container</code> set to <code>@list</code> and <em>value</em> is <tref>null</tref>,
+ continue to the next <em>term</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>term</em> has a <code>@container</code> set to <code>@list</code>,
+ continue to the next <em>term</em>.</li>
+ <li>Set <em>rank</em> to the <tref>term rank</tref> of <em>value</em> by passing
+ passing <em>term</em>, <em>value</em>, and <tref>active context</tref> to
+ the <a href="#term-rank-algorithm">Term Rank Algorithm</a>.</li>
+ <li>If <em>rank</em> is greater than <code>0</code>:
+ <ol class="algorithm">
+ <li>If <em>term</em> has a <code>container</code> set to <code>@set</code>, then add
+ <code>1</code> to <em>rank</em>.</li>
+ <li>If <em>value</em> is a <tref>JSON object</tref> containing only the property <code>@list</code>
+ and <em>list container</em> is <code>false</code> and <em>term</em> has a <code>container</code>
+ set to <code>@list</code>, then set <em>list container</em> to <code>true</code>, clear
+ <em>terms</em>, set <em>highest rank</em> to <em>rank</em>, and add <em>term</em> to <em>terms</em>.</li>
+ <li>Otherwise, if <em>rank</em> is greater than or equal to <em>highest rank</em>:
+ <ol class="algorithm">
+ <li>If <em>rank</em> is greater than <em>highest rank</em>, clear <em>terms</em> and set
+ <em>highest rank</em> to <em>rank</em>.</li>
+ <li>Add <em>term</em> to <em>terms</em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <em>terms</em> is empty, and the <tref>active context</tref> has a <code>@vocab</code>
+ which is a prefix of <em>iri</em> where
+ the resulting <tref>relative IRI</tref> is not a <tref>term</tref> in the
+ <tref>active context</tref>. The resulting <tref>relative IRI</tref> is the
+ unmatched part of <em>iri</em>.</li>
+ <li>If <em>terms</em> is empty, add a <tref>compact IRI</tref> representation of <em>iri</em>
+ for each <tref>term</tref> in the <tref>active context</tref> which
+ maps to an <tref>IRI</tref> which is a prefix for <em>iri</em> where
+ the resulting <tref>compact IRI</tref> is not a <tref>term</tref> in the
+ <tref>active context</tref>. The resulting <tref>compact IRI</tref> is the
+ <tref>term</tref> associated with the partially
+ matched IRI in the <tref>active context</tref> concatenated with a
+ colon (:) character and the unmatched part of <em>iri</em>.</li>
+ <li>If <em>terms</em> is empty, the <tref>IRI</tref> being processed is a property or the
+ value of <code>@type</code> and <code>@vocab</code> is not null and matches the beginning
+ of <em>iri</em>, return the unmatched portion of <em>iri</em>. Otherwise return
+ <em>iri</em>.</li>
+ <li>Otherwise, return the shortest and lexicographically least value in <em>terms</em>.</li>
+ </ol>
+ </p>
+</section>
+
+<section>
+ <h3>IRI Compaction Algorithm</h3>
+ <p>The algorithm for generating a <tref>compact IRI</tref> is:
+ <ol class="algorithm">
+ <li>Create an empty list of terms <em>terms</em> that will be populated with
+ <tref>term</tref>s that are ranked according to how closely they match
+ <em>value</em>. Initialize <em>highest rank</em> to <code>0</code>,
+ and set a flag <em>list container</em> to <code>false</code>.</li>
+ <li>For each <em>term</em> in the <tref>active context</tref>:
+ <ol class="algorithm">
+ <li>If the <em>term</em>'s <tref>IRI</tref> is not a complete match against
+ <em>iri</em>, continue to the next <em>term</em>.</li>
+ <li>If <em>value</em> is a <tref>JSON object</tref> containing only the property <code>@list</code>:
+ <ol class="algorithm">
+ <li>If <em>term</em> has a <code>@container</code> set to <code>@set</code>, continue
+ to the next <em>term</em>.</li>
+ <li>If <em>list container</em> is <code>true</code> and <em>term</em> does not have a
+ <code>container</code> set to <code>@list</code> and <em>value</em> is <tref>null</tref>,
+ continue to the next <em>term</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>term</em> has a <code>container</code> set to <code>@list</code>,
+ continue to the next <em>term</em>.</li>
+ <li>Set <em>rank</em> to the <tref>term rank</tref> of <em>value</em> by passing
+ passing <em>term</em>, <em>value</em>, and <tref>active context</tref> to
+ the <a href="#term-rank-algorithm">Term Rank Algorithm</a>.</li>
+ <li>If <em>rank</em> is greater than <code>0</code>:
+ <ol class="algorithm">
+ <li>If <em>term</em> has a <code>container</code> set to <code>@set</code>, then add
+ <code>1</code> to <em>rank</em>.</li>
+ <li>If <em>value</em> is a <tref>JSON object</tref> containing only the property <code>@list</code>
+ and <em>list container</em> is <code>false</code> and <em>term</em> has a <code>container</code>
+ set to <code>@list</code>, then set <em>list container</em> to <code>true</code>, clear
+ <em>terms</em>, set <em>highest rank</em> to <em>rank</em>, and add <em>term</em> to <em>terms</em>.</li>
+ <li>Otherwise, if <em>rank</em> is greater than or equal to <em>highest rank</em>:
+ <ol class="algorithm">
+ <li>If <em>rank</em> is greater than <em>highest rank</em>, clear <em>terms</em> and set
+ <em>highest rank</em> to <em>rank</em>.</li>
+ <li>Add <em>term</em> to <em>terms</em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <em>terms</em> is empty, and the <tref>active context</tref> has a <code>@vocab</code>
+ which is a prefix of <em>iri</em> where
+ the resulting <tref>relative IRI</tref> is not a <tref>term</tref> in the
+ <tref>active context</tref>. The resulting <tref>relative IRI</tref> is the
+ unmatched part of <em>iri</em>, unless the <tref>relative IRI</tref> is also a term in the
+ <tref>active context</tref>.</li>
+ <li>If <em>terms</em> is empty, add a <tref>compact IRI</tref> representation of <em>iri</em>
+ for each <tref>term</tref> in the <tref>active context</tref> which
+ maps to an <tref>IRI</tref> which is a prefix for <em>iri</em> where
+ the resulting <tref>compact IRI</tref> is not a <tref>term</tref> in the
+ <tref>active context</tref>. The resulting <tref>compact IRI</tref> is the
+ <tref>term</tref> associated with the partially
+ matched IRI in the <tref>active context</tref> concatenated with a
+ colon (:) character and the unmatched part of <em>iri</em>.</li>
+ <li>If <em>terms</em> is empty, the <tref>IRI</tref> being processed is a property or the
+ value of <code>@type</code> and <code>@vocab</code> is not null and matches the beginning
+ of <em>iri</em>, return the unmatched portion of <em>iri</em>. Otherwise return
+ <em>iri</em>.</li>
+ <li>Otherwise, return the shortest and lexicographically least value in <em>terms</em>.</li>
+ </ol>
+ </p>
+</section>
+
+<section>
+<h3>Term Rank Algorithm</h3>
+<p>When selecting among multiple possible terms for a given property, it may be that multiple
+ <tref title="term">terms</tref> are defined with the same <tref>IRI</tref>, but differ in <code>@type</code>, <code>@container</code>
+ or <code>@language</code>. The purpose of this algorithm is to take a <tref>term</tref>
+ and a value and give it a <tdef>term rank</tdef>. The selection can then be based, partly, on
+ the term having the highest <tref>term rank</tref>.</p>
+<p>Given a <tref>term</tref> <em>term</em>, <em>value</em>, and <tref>active context</tref>
+ determine the <tref>term rank</tref> using the following steps:</p>
+<ol class="algorithm">
+ <li>If <em>value</em> is <tref>null</tref>, <tref>term rank</tref> is <code>3</code>.</li>
+ <li>Otherwise, if <em>value</em> is a <tref>JSON object</tref> containing only the property <code>@list</code>:
+ <ol class="algorithm">
+ <li>If the <code>@list</code> property is an empty array, if <em>term</em> has <code>@container</code>
+ set to <code>@list</code>, <tref>term rank</tref> is <code>1</code>, otherwise <code>0</code>.</li>
+ <li>Otherwise, return the sum of the <tref>term rank</tref>s for every entry in the list.</li>
+ </ol>
+ </li>
+ <li>Otherwise, <em>value</em> MUST be a <tref>node object</tref>,
+ or a <tref>JSON object</tref> having a <code>@value</code>.
+ <ol class="algorithm">
+ <li>If <em>value</em> has a <code>@value</code> property:
+ <ol class="algorithm">
+ <li>If <em>value</em> has a <code>@type</code> property: if that type matches a
+ <code>@type</code> coercion for <em>term</em>, <tref>term rank</tref>
+ is <code>3</code>, otherwise if <em>term</em> has no <code>@type</code>
+ coercion and no <code>@language</code>, <tref>term rank</tref> is
+ <code>1</code>, otherwise <code>0</code>.</li>
+ <li>Otherwise, if <code>@value</code> is not a <tref>string</tref>: if <em>term</em> has
+ no <code>@type</code> or <code>@language</code> it is <code>2</code>, otherwise <code>1</code>.</li>
+ <li>Otherwise, if <em>value</em> has no <code>@language</code> property: if <em>term</em> has
+ <code>@language</code> <tref>null</tref> or ((<em>term</em> has no <code>@type</code> or
+ <code>@language</code>) and the <tref>active context</tref> has no <code>@language</code>),
+ <tref>term rank</tref> is <code>3</code>, otherwise <code>0</code>.</li>
+ <li>Otherwise, if <em>value</em> has only a <code>@value</code> and <code>@language</code> property
+ and <em>term</em> has a <code>@container</code> key associated with a value of
+ <code>@language</code> in the <tref>active context</tref>,
+ <tref>term rank</tref> is <code>1</code>,
+ otherwise <code>-Infinity</code>.</li>
+ <li>Otherwise, if <em>value</em> has a <code>@language</code> property matching a
+ <code>@language</code> definition for <em>term</em> or
+ ((<em>term</em> has no <code>@type</code> or <code>@language</code> definition) and
+ <code>@language</code> in the <tref>active context</tref> matches the
+ <em>value</em> <code>@language</code>), <tref>term rank</tref> is
+ <code>3</code>, otherwise if <em>term</em> has no <code>@type</code>
+ coercion and no <code>@language</code>, <tref>term rank</tref> is
+ <code>1</code>, otherwise <code>0</code>.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>term</em> has <code>@type</code> coerced to <code>@id</code>,
+ <tref>term rank</tref> is <code>3</code>, otherwise
+ if <em>term</em> has no <code>@type</code> coercion and no <code>@language</code>,
+ <tref>term rank</tref> is <code>1</code>, otherwise <code>0</code>.</li>
+ </ol>
+ </li>
+ <li>Return <tref>term rank</tref>.</li>
+</ol>
+</section>
+
+<section>
+ <h2>Value Compaction</h2>
+ <p>Some values, such as <tref title="IRI">IRIs</tref> and <tref title="typed value">typed values</tref>, may be expressed in an
+ <tref>expanded form</tref> (<tdef>expanded value</tdef>) in JSON-LD. These values are required to be compacted at
+ times when processing JSON-LD documents. A value is said to be in <tdef>compacted form</tdef> after
+ the application of this algorithm on an <tref>expanded value</tref>.
+ </p>
+
+ <p>The algorithm for compacting an <tref>expanded value</tref> <em>value</em> takes an <tref>active property</tref>
+ and <tref>active context</tref>. It is implemented as follows:</p>
+ <ol class="algorithm">
+ <li>If <em>value</em> only has one property and the <tref>active context</tref> has no default language,
+ then the compacted value is the value of <code>@value</code>.</li>
+ <li>Otherwise, if <tref>active property</tref> is <code>@graph</code>, the compacted value is the
+ value associated with the <code>@id</code> key, processed according to
+ the <a href="#iri-compaction">IRI Compaction</a> steps.</li>
+ <li>Otherwise, if the <tref>active context</tref> contains a coercion target for the
+ key that matches the expression of the value, compact the value using the
+ following steps:
+ <ol class="algorithm">
+ <li>If the coercion target is an <code>@id</code>, the compacted
+ value is the value associated with the <code>@id</code> key,
+ processed according to the
+ <a href="#iri-compaction">IRI Compaction</a> steps.</li>
+ <li>If the coercion target is a <tref>typed value</tref>, the compacted
+ value is the value associated with the <code>@value</code> key.</li>
+ </ol>
+ </li>
+ <li>Otherwise, if <em>value</em> contains an <code>@id</code> key, the compacted value is <em>value</em> with
+ the value of <code>@id</code> processed according to the
+ <a href="#iri-compaction">IRI Compaction</a> steps.</li>
+ <li>Otherwise, if the <tref>active context</tref> contains a <code>@language</code>, which
+ matches the <code>@language</code> of the value, or the value has only a <code>@value</code> key, the compacted
+ value is the value associated with the <code>@value</code> key.</li>
+ <li>Otherwise, if the value contains a <code>@type</code> key, the compacted value
+ is <em>value</em> with the <code>@type</code> value processed according to the
+ <a href="#iri-compaction">IRI Compaction</a> steps.</li>
+ <li>Otherwise, the value is not modified.</li>
+ </ol>
+</section>
+
+<section>
+ <h2>Find and Remove Property Generator Duplicates</h2>
+
+ <p>This algorithm checks if a specific value exists for all <tref title="IRI">IRIs</tref>
+ associated with a <tref>property generator</tref> and if so, it removes them. The
+ algorithm takes five parameters: <em>element</em>, <em>property</em>, <em>value</em>,
+ <tref>active context</tref>, <tref>active property</tref>.</p>
+
+ <ol class="algorithm">
+ <li>For each item <em>propertyGenerator</em> of the <tref>array</tref> which is the
+ value of the <code>propertyGenerators</code> member of <tref>active property</tref> perform
+ the following steps:
+ <ol class="algorithm">
+ <li>Check that a member exists for each <tref>IRI</tref> associated with the
+ <em>propertyGenerator</em>. If <em>value</em> is not <tref>null</tref> also check
+ whether each of those members that contains <em>value</em>. Values are considered to be equal
+ if they are of the same type and have the same value(s); <tref title="node object">node objects</tref>
+ are considered to be equal if all members match, except if no <code>@id</code> member exists (i.e., it is
+ an unlabeled <tref>blank node</tref>, in that case <tref title="node object">node objects</tref> are never
+ considered to be equal.
+ </li>
+ <li>If that's not the case, continue with the next <em>propertyGenerator</em>.</li>
+ <li>Otherwise, remove <em>value</em> from every member. If the resulting value
+ of a member is an empty <tref>array</tref>, remove the member altogether
+ from <em>element</em>.</li>
+ <li>Return <em>propertyGenerator</em>.</li>
+ </ol>
+ </li>
+ <li>Return the value of the <code>term</code> member of <tref>active property</tref>
+ since no matching <tref>property generator</tref> has been found.</li>
+ </ol>
+</section>
+
+<section>
+ <h2>Flattening Algorithm</h2>
+
+ <p>The algorithm takes two input variables, an <em>element</em> to flatten and a
+ <em>context</em> used to compact the flattened document.</p>
+
+ <ol class="algorithm">
+ <li>Expand <em>element</em> according the
+ <a href="#expansion-algorithm">Expansion algorithm</a>.</li>
+ <li>Generate a <em>nodeMap</em> according the
+ <a href="#node-map-generation">Node Map Generation algorithm</a>.</li>
+ <li>Let <em>defaultGraph</em> be the value of the <code>@default</code> member of
+ <em>nodeMap</em>; a <tref>JSON object</tref> representing the <tref>default graph</tref>.</li>
+ <li>For each other <em>graphName</em>-<em>graph</em> pair in <em>nodeMap</em>
+ perform the following steps:
+ <ol class="algorithm">
+ <li>If <em>defaultGraph</em> does not have a <em>graphName</em> member, create
+ one and initialize its value to a <tref>JSON object</tref> consisting of an
+ <code>@id</code> member whose value is set to <em>graphName</em>.</li>
+ <li>Add a <code>@graph</code> member set to an empty <tref>array</tref>
+ (referred to as <em>nodes</em>) to the <tref>JSON object</tref> which is the
+ value of the <em>graphName</em> member of <em>nodeMap</em>.</li>
+ <li>For each <em>id</em>-<em>node</em> pair in <em>graph</em> ordered by <em>id</em>,
+ add <em>node</em> to the <em>nodes</em> <tref>array</tref>.</li>
+ </ol>
+ </li>
+ <li>Initialize an empty <tref>array</tref> flattened.</li>
+ <li>For each <em>id</em>-<em>node</em> pair in <em>defaultGraph</em> ordered by <em>id</em>,
+ add <em>node</em> to <em>flattened</em>.</li>
+ <li>If <em>context</em> equals <tref>null</tref>, return <em>flattened</em>.</li>
+ <li>Otherwise, return the result of compacting <em>flattened</em> according the
+ <a href="#compaction-algorithm">Compaction algorithm</a> passing <em>context</em>
+ ensuring that the compaction result uses the <code>@graph</code> keyword (or its alias)
+ at the top-level, even if the context is empty or if there is only one element to
+ put in the <code>@graph</code> <tref>array</tref>. This ensures that the returned
+ document has a deterministic structure.</li>
+ </ol>
+</section>
+
+<section>
+ <h2>Node Map Generation</h2>
+ <p>The Node Map Generation algorithm takes as input an expanded JSON-LD document and results in a <tref>JSON object</tref>
+ <em>nodeMap</em> holding a flat representation of the graphs and <tref title="node">nodes</tref> represented in the document. All <tref title="node">nodes</tref> that are not
+ uniquely identified by an IRI get assigned a (new) <tref>blank node identifier</tref>. The resulting <em>nodeMap</em>
+ document will have a property for every graph in the document whose value is another object with a property for every
+ <tref>node</tref> represented in the document. While the default graph is stored under the <code>@default</code> property and the merged graph
+ under the <code>@merged</code> property, all other graphs are stored under their respective <tref title="IRI">IRIs</tref>.</p>
+
+ <p>The algorithm takes as input the expanded JSON-LD document as <em>element</em>, the initially empty <em>nodeMap</em>,
+ <code>@default</code> as <em>graph</em>, <tref>null</tref> as <em>list</em>, and <tref>null</tref> as <em>id</em>.</p>
+
+ <ol class="algorithm">
+ <li>If <em>element</em> is an array, process each entry in <em>element</em> recursively, using this algorithm
+ and return.</li>
+ <li>If <em>element</em> is not a <tref>JSON object</tref> or if it has a <code>@value</code> property,
+ then if <em>list</em> is not <tref>null</tref>, append <em>element</em> to <em>list</em> and return.</li>
+ <li>If <em>id</em> is <tref>null</tref> and if the <code>@id</code>
+ property exists and is an <tref>IRI</tref>, set <em>id</em> to its value,
+ otherwise set it to a <tref>blank node identifier</tref> created by the
+ <a href="#generate-blank-node-identifier">Generate Blank Node Identifier</a>
+ algorithm.</li>
+ <li>If <em>list</em> is not <tref>null</tref>, append a new <tref>node object</tref> to <em>list</em> using
+ <em>id</em> as the value for <code>@id</code>.</li>
+ <li>Let <em>nodes</em> be the value in <em>nodeMap</em> where the key is <em>graph</em>; if no such
+ value exists, insert a new <tref>JSON object</tref> for the key <em>graph</em>. If <em>id</em> is not in
+ <em>nodes</em>, create a new <tref>JSON object</tref> <em>node</em> with <em>id</em> as the value
+ for <code>@id</code>. Let <em>node</em> be the value of <em>id</em> in <em>nodes</em>.</li>
+ <li>For each <em>property</em> that is not <code>@id</code> and each <em>value</em> in <em>element</em> ordered
+ by <em>property</em>:
+ <ol class="algorithm">
+ <li>If <em>property</em> is <code>@graph</code>, recursively call this algorithm passing <em>value</em>
+ for <em>element</em>, <em>nodeMap</em>, <tref>null</tref> for <em>list</em> and if <em>graph</em>
+ is <code>@merged</code> use <em>graph</em>, otherwise use <em>id</em> for <em>graph</em> and then continue.</li>
+ <li>If <em>property</em> is not <code>@type</code> and is a keyword, merge <code>property</code> and
+ <code>value</code> into <code>node</code> and then continue.</li>
+ <li>For each value <em>v</em> in the array <em>value</em>:
+ <ol class="algorithm">
+ <li>If <em>v</em> is a <tref>node object</tref> or <tref>node object</tref>:
+ <ol class="algorithm">
+ <li>If the property <code>@id</code> is not an <tref>IRI</tref> or it does not exist,
+ map <em>v</em> to a <a
+ href="#generate-blank-node-identifier">new blank node
+ identifier</a> <em>name</em> to avoid collisions. If one does
+ not already exist, add a <tref>node object</tref> for
+ <em>v</em> into <em>node</em> for <em>property</em>.</li>
+ <li>Recursively call this algorithm passing <em>v</em> for <em>value</em>, <em>nodeMap</em>,
+ <em>graph</em>, <tref>null</tref> for <em>list</em>, and <em>name</em> for <em>id</em>.</li>
+ </ol>
+ </li>
+ <li>Otherwise if <em>v</em> has the property <code>@list</code> then recursively call this algorithm
+ with the value of <code>@list</code> as <em>element</em>, <em>nodeMap</em>, <em>graph</em>, and
+ a new array <em>flattenedList</em> as <em>list</em>. Create a new <tref>JSON object</tref> with the
+ property <code>@list</code> set to <em>flattenedList</em> and add it to <em>node</em> for
+ <em>property</em>.</li>
+ <li>Otherwise, if <em>property</em> is <code>@type</code> and <em>v</em> is not an <tref>IRI</tref>,
+ generate a <a href="#generate-blank-node-identifier">new blank node identifier</a> and add it
+ to <em>node</em> for <em>property</em>.</li>
+ <li>Otherwise, add <em>v</em> to <em>node</em> for <em>property</em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>After the above outlined algorithm has been executed, the node map for all graphs including the default graph are contained in
+ <em>nodeMap</em>. To also create the node map for the merged graph, execute the algorithm again, but pass <code>@merged</code>
+ for <em>graph</em>.</p>
+</section>
+
+ <section>
+ <h2>RDF Conversion Algorithms</h2>
+
+ <p>This specification describes algorithms to transform JSON-LD documents to an array of
+ RDF <tref title="quad">quads</tref> and vice-versa. Note that many uses of JSON-LD
+ may not require generation of RDF.</p>
+
+ <p>The processing algorithms described in this section are 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 <tref title="quad">quads</tref> but are
+ not required to implement the algorithm exactly as described.</p>
+
+ <p class="issue">This algorithm hasn't been updated yet.</p>
+
+ <section>
+ <h3>Convert to RDF Algorithm</h3>
+ <p>
+ The algorithm below is designed for in-memory implementations with random access to <tref>JSON object</tref> elements.
+ </p>
+ <p>
+ A conforming JSON-LD processor implementing RDF conversion MUST implement a
+ processing algorithm that results in the same set of RDF <tref title="quad">quads</tref> that the following
+ algorithm generates:
+ </p>
+
+ <p>The algorithm takes four input variables: a <em>element</em> to be converted, an
+ <tref>active subject</tref>, <tref>active property</tref> and <tref>graph name</tref>.
+ To begin, the <tref>active subject</tref>, <tref>active property</tref> and <tref>graph name</tref>
+ are set to <tref>null</tref>, and <em>element</em> is
+ set to the result of performing the <a href="#expansion-algorithm">Expansion Algorithm</a> on
+ the <tref>JSON-LD input</tref> which is expected to be a a well-formed JSON-LD document as defined in [[!JSON-LD]].
+ This removes any existing context to allow the given context to be cleanly applied.</p>
+
+ <ol class="algorithm">
+ <li id="processing-step-associative">
+ If <em>element</em> is a <tref>JSON object</tref>, perform the following steps:
+ <ol class="algorithm">
+ <li>Set <tref>active object</tref> to <tref>null</tref>.</li>
+ <li>
+ If <em>element</em> has a <code>@value</code> property:
+ <ol class="algorithm">
+ <li>If the value of <code>@value</code> is a <tref>number</tref>, set the
+ <tref>active object</tref> to a <tref>typed value</tref> using a <tref>canonical lexical form</tref>
+ of the value as defined in the section <a href="#data-round-tripping">Data Round Tripping</a>.
+ Set datatype to the value of the <code>@type</code> property if it exists, otherwise
+ either <code>xsd:integer</code> or <code>xsd:double</code>, depending
+ on if the value contains a fractional and/or an exponential component.</li>
+ <li>Otherwise, if the value of <code>@value</code> is <strong>true</strong> or <strong>false</strong>,
+ set the <tref>active object</tref> to a <tref>typed value</tref> created from the
+ <tref>canonical lexical form</tref> of the value. Set datatype to the value of the <code>@type</code>
+ property if it exists, otherwise <code>xsd:boolean</code>.</li>
+ <li>
+ Otherwise, if <em>element</em> contains a <code>@type</code> property, set the
+ <tref>active object</tref> to a <tref>typed value</tref>.
+ </li>
+ <li>
+ Otherwise, if <em>element</em> contains a <code>@language</code> property, set the
+ <tref>active object</tref> to a <tref>language-tagged string</tref>.
+ </li>
+ <li>
+ Otherwise, set the <tref>active object</tref> to a <tref>typed value</tref>
+ using <code>xsd:string</code> as the datatype.
+ </li>
+ </ol>
+ </li>
+ <li>
+ If <em>element</em> has a <code>@list</code> property the value MUST be an <tref>array</tref>.
+ Process its value as a list as described in <a href="#list-conversion">List Conversion</a> using
+ the return value as the <tref>active object</tref>
+ </li>
+ <li>If <tref>active object</tref> is not <tref>null</tref>:
+ <ol class="algorithm">
+ <li>If neither <tref>active subject</tref> nor <tref>active property</tref> are <tref>null</tref>,
+ generate a <tref>Quad</tref>
+ representing <tref>active subject</tref>, <tref>active property</tref>,
+ <tref>active object</tref>, and <tref>graph name</tref>.</li>
+ <li>Return <tref>active object</tref>.</li>
+ </ol>
+ </li>
+ <li id="processing-step-subject">If <em>element</em> has a <code>@id</code> property,
+ the value MUST be a <tref>string</tref>, set the <tref>active subject</tref> to the previously
+ expanded value (either a <tref>blank node</tref> or an <tref>IRI</tref>).</li>
+ <li>
+ Otherwise, if <em>element</em> does not have a <code>@id</code> property, set the <tref>active
+ subject</tref> to newly generated <tref>blank node</tref>.</li>
+ <li>
+ Process each <em>property</em> and <em>value</em> in <em>element</em>, ordered by
+ <em>property</em>, as follows:
+ <ol class="algorithm">
+ <li>
+ If <em>property</em> is <code>@type</code>, set the <tref>active property</tref>
+ to <code>rdf:type</code>.
+ </li>
+ <li>Otherwise, if <em>property</em> is <code>@graph</code>,
+ process <em>value</em> algorithm recursively, using <tref>active subject</tref> as <tref>graph name</tref>
+ and null values for <tref>active subject</tref> and <tref>active property</tref> and then
+ proceed to next property.</li>
+ <li>Otherwise, if <em>property</em> is a <tref>keyword</tref>, skip this step.</li>
+ <li>Otherwise, set <tref>active property</tref> to the <tref>expanded IRI form</tref> of <em>property</em>.</li>
+ <li>Process <em>value</em> recursively using this algorithm, passing copies of
+ <tref>active subject</tref>, <tref>active property</tref> and <tref>graph name</tref>.
+ </li>
+ </ol>
+ </li>
+ <li>
+ Set <tref>active object</tref> to <tref>active subject</tref>.
+ </li>
+ </ol>
+ </li>
+
+ <li>Otherwise, if <em>element</em> is an <tref>array</tref>, process each value in the <tref>array</tref>
+ as follows, process <em>element</em> recursively using this algorithm, using copies of
+ <tref>active subject</tref>, <tref>active property</tref>, and <tref>graph name</tref>.</li>
+
+ <li>Otherwise, if <em>element</em> is a <tref>string</tref>, then the <tref>active property</tref>
+ must be <code>rdf:type</code> so set the <tref>active object</tref> to an <tref>IRI</tref>.</li>
+
+ <li>If any of these steps created an <tref>active object</tref> and neither <tref>active subject</tref>
+ nor <tref>active property</tref> are <tref>null</tref>, generate a <tref>Quad</tref> using
+ <tref>active subject</tref>,<tref>active property</tref>, <tref>active object</tref> and
+ <tref>graph name</tref>.
+ </li>
+ <li>Return <tref>active object</tref>.</li>
+ </ol>
+ </section>
+
+ <section id="list-conversion">
+ <h3>List Conversion</h3>
+
+ <p>List Conversion is the process of taking an <tref>array</tref> of values and adding them to a newly
+ created <cite><a href="http://www.w3.org/TR/rdf-schema/#ch_collectionvocab">RDF Collection</a></cite> (see
+ [[!RDF-SCHEMA]]) 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:</p>
+ <p>The algorithm is invoked with an <tref>array</tref> <em>array</em>, the <tref>active property</tref>
+ and returns a value to be used as an <tref>active object</tref> in the calling location.</p>
+ <div class="note">This algorithm does not support lists containing lists.</div>
+
+ <p class="issue">This algorithm hasn't been updated yet.</p>
+
+ <ol class="algorithm">
+ <li>
+ If <em>array</em> is empty return <code>rdf:nil</code>.
+ </li>
+ <li>
+ Otherwise, generate a <tref>Quad</tref> using using the <tref>active subject</tref>, <tref>active property</tref>
+ and a newly generated <tref>blank node</tref> identified as <em>first <tref>blank node</tref></em>.
+ </li>
+ <li>
+ For each element in <em>array</em> other than the last element:
+ <ol class="algorithm">
+ <li>Create a processor state using
+ <em>first blank node</em> as the <tref>active subject</tref>, and
+ <code>rdf:first</code> as the <tref>active property</tref>.
+ <ol class="algorithm">
+ <li>Process the value starting at <a href="#processing-step-associative">Step 1</a>.</li>
+ <li>Proceed using the previous <tref>processor state</tref>.</li>
+ </ol>
+ </li>
+ <li>Unless this is the last element in <em>array</em>, generate a new <tref>blank node</tref> identified as
+ <em>rest blank node</em>, otherwise use <code>rdf:nil</code>.</li>
+ <li>Generate a new <tref>Quad</tref> using <em>first blank node</em>,
+ <code>rdf:rest</code> and <em>rest blank node</em>.</li>
+ <li>Set <em>first blank node</em> to
+ <em>rest blank node</em>.</li>
+ <li>Return <em>first blank node</em>.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section>
+ <h2>Convert from RDF Algorithm</h2>
+ <p>In some cases, data exists natively in the form of triples or or <tref title="quad">quads</tref>;
+ for example, if the data was originally represented in an RDF graph or triple/quad store. This
+ algorithm is designed to simply translate an array of <tref title="quad">quads</tref> into a
+ JSON-LD document.</p>
+ <p>When expanding <tref title="typed value">typed values</tref> having a datatype of <code>xsd:string</code>,
+ the <code>@type</code> MUST NOT be set to <code>xsd:string</code> and the resulting value
+ MUST have only a <code>@value</code> property.</p>
+
+ <p>The conversion algorithm takes a single parameter <em>input</em> in the form of an
+ array of <tref>Quad</tref> representations.</p>
+
+ <p class="issue">This algorithm hasn't been updated yet.</p>
+
+ <ol class="algorithm">
+ <li id="new_graph">Construct <em>defaultGraph</em> as a <tref>JSON object</tref>
+ containing <em>nodes</em> and <em>listMap</em>, each an empty <tref>JSON object</tref>.</li>
+ <li>Construct <em>graphs</em> as a <tref>JSON object</tref> containing <em>defaultGraph</em>
+ identified by
+ an empty <tref>string</tref>.</li>
+ <li>For each <tref>quad</tref> in <em>input</em>:
+ <ol class="algorithm">
+ <li>Set <em>graph</em> to the entry in <em>graphs</em> identified
+ by <em>name</em>, initializing it to a new entry using the mechanism
+ described in <a href="#new_graph">Step 1</a>.</li>
+ <li>If <em>property</em> is <code>rdf:first</code>,
+ use the entry in <em>graph.listMap</em> indexed by <em>subject</em>,
+ initializing it to a new <tref>JSON object</tref> if nesessary. Represent
+ <em>object</em> in <tref>expanded form</tref>, as described in
+ <a href="#value-expansion">Value Expansion</a>. Add the
+ resulting <em>object representation</em> to the entry indexed by
+ <em>first</em>, and skip to the next <tref>quad</tref>.</li>
+ <li>If <em>property</em> is <code>rdf:rest</code>:
+ <ol class="algorithm">
+ <li>If <em>object</em> is a <tref>blank node</tref>, use the entry in
+ <em>graph.listMap</em> indexed by <em>subject</em>, initializing it
+ to a new <tref>JSON object</tref> if necessary. Add the <em>nominalValue</em> of
+ <em>object</em> to the entry indexed by <em>rest</em>.
+ </li>
+ <li>Skip to the next <tref>quad</tref>.</li>
+ </ol>
+ </li>
+ <li>If <em>name</em> is not <tref>null</tref>, and <em>defaultGraph.nodes</em>
+ does not contain an entry for <em>name</em>,
+ create a new entry for <em>name</em> from a new
+ <tref>JSON object</tref> with key/value pair of <code>@id</code> and
+ <em>name</em> represented in <tref>expanded IRI form</tref>.</li>
+ <li>Set <em>value</em> as the entry from <em>graph.nodes</em> for
+ <em>subject</em>, initializing it to a new
+ <tref>JSON object</tref> with key/value pair of <code>@id</code> and
+ <em>subject</em> represented in <tref>expanded IRI form</tref> if necessary.</li>
+ <li>If <em>property</em> is <code>rdf:type</code>, <em>object</em> is not a <tref>JSON-LD value</tref>, and the
+ <code class="idlMemberName"><a href="#widl-JsonLdOptions-useRdfType">useRdfType</a></code>
+ option is not present or <tref>false</tref>:
+ <ol class="algorithm">
+ <li>Append <em>object</em> represented in <tref>expanded IRI form</tref> to the array value for the
+ key <code>@type</code>, creating an entry in <em>value</em> if necessary.</li>
+ </ol>
+ </li>
+
+ <li>Otherwise, if <em>object</em> is a <tref>typed value</tref> and the
+ <code class="idlMemberName"><a href="#widl-JsonLdOptions-useNativeTypes">useNativeTypes</a></code>
+ option is set to <tref>true</tref>:
+ <ol class="algorithm">
+ <li>Generate a <em>converted value</em>:
+ <ol class="algorithm">
+ <li>If the literal's type is <code>xsd:boolean</code>, the
+ <em>converted value</em> is <tref>true</tref> if the literal
+ matches the value <code>true</code> or <code>false</code> if
+ the literal matches the value <code>false</code>.</li>
+ <li>If the literal's type is <code>xsd:integer</code> or
+ <code>xsd:double</code>, try to convert the literal to a
+ JSON <tref>number</tref>. If the conversion is successful,
+ store the result in <em>converted value</em>, otherwise
+ set <em>converted value</em> to <em>value</em>.</li>
+ <li>Otherwise, do not perform a conversion. Set
+ the <em>converted value</em> to the <em>value</em>.</li>
+ </ol>
+ </li>
+ <li>Append the <em>converted value</em> to the array value for the
+ key, creating an entry in <em>value</em> if necessary.</li>
+ </ol>
+ </li>
+
+ <li>Otherwise, if <em>object</em> is <code>rdf:nil</code>:
+ <ol class="algorithm">
+ <li>Let <em>key</em> be <em>property</em> expressed in <tref>expanded IRI form</tref>.</li>
+ <li>Append an empty <code>@list</code> representation to the array value for
+ <em>key</em>, creating an entry in <em>value</em> if necessary.</li>
+ </ol>
+ </li>
+ <li>Otherwise,
+ <ol class="algorithm">
+ <li>Let <em>key</em> be <em>property</em> expressed in <tref>expanded IRI form</tref> and let
+ <em>object representation</em>
+ be <em>object</em> represented in <tref>expanded form</tref> as described in
+ <a href="#value-expansion">Value Expansion</a>.</li>
+ <li>If <em>object</em> is a <tref>blank node</tref>,
+ use the entry in <em>graph.listMap</em> indexed by <em>object</em>,
+ initializing it to a new <tref>JSON object</tref> if nesessary.
+ Add an entry for <em>head</em> with <em>object representation</em>.</li>
+ <li>Append <em>object representation</em> to the array value for
+ <em>key</em>, creating an entry in <em>value</em> if necessary.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each <em>name</em> and <em>graph</em> in <em>graphs</em>:
+ <ol class="algorithm">
+ <li>For each <em>subject</em> and <em>entry</em> in <em>graph</em>
+ where <em>entry</em> has both <em>head</em> and <em>first</em> keys:
+ <ol class="algorithm">
+ <li>Set <em>value</em> to the value of <em>head</em> in <em>entry</em>.</li>
+ <li>Remove the entry for <code>@id</code> in <em>value</em>.</li>
+ <li>Add an entry to <em>value</em> for <code>@list</code> initialized to a new array
+ containing the value of <em>first</em> from <em>entry</em>.</li>
+ <li>While <em>entry</em> has a key for <em>rest</em>:
+ <ol class="algorithm">
+ <li>Set <em>entry</em> to the value of <em>graph.listMap</em> for <em>entry.rest</em>.</li>
+ <li>Add the value for <em>entry.first</em> to the list array.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Create <em>array</em> as an empty <tref>array</tref>.</li>
+ <li>For each <em>subject</em> and <em>entry</em> in <em>defaultGraph.nodes</em>
+ ordered by <em>subject</em>:
+ <ol class="algorithm">
+ <li>Add <em>entry</em> to <em>array</em>.</li>
+ <li>If <em>graphs</em> has an entry for <em>subject</em>, add a property
+ <code>@graph</code> in <em>entry</em> containing the ordered entries
+ from <em>graphs[subject].nodes</em>.</li>
+ </ol>
+ </li>
+ <li>Return <em>array</em> as the result.</li>
+ </ol>
+ </section>
+
+ <section>
+ <h3>Data Round Tripping</h3>
+
+ <p>When <a href="#rdf-conversion">converting JSON-LD to RDF</a> JSON-native types such as
+ <em>numbers</em> and <em>booleans</em> are automatically coerced to <strong>xsd:integer</strong>,
+ <strong>xsd:double</strong>, or <strong>xsd:boolean</strong>. Implementers MUST ensure that the
+ result is in <tref>canonical lexical form</tref>. A
+ <tdef>canonical lexical form</tdef> is a set of literals from among the valid set of literals for
+ a datatype such that there is a one-to-one mapping between the <tref>canonical lexical form</tref> and a value
+ in the value space as defined in [[!XMLSCHEMA11-2]]. In other words, every value MUST be converted
+ to a deterministic <tref>string</tref> representation.</p>
+
+ <p>The canonical lexical form of an <em>integer</em>, i.e., a number without fractions
+ or a number coerced to <strong>xsd:integer</strong>, is a finite-length sequence of decimal
+ digits (<code>0-9</code>) with an optional leading minus sign; leading zeroes are prohibited.
+ To convert the number in JavaScript, implementers can use the following snippet of code:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ (value).toFixed(0).toString()
+ -->
+ </pre>
+
+ <p>The canonical lexical form of a <em>double</em>, i.e., a number with fractions
+ or a number coerced to <strong>xsd:double</strong>, consists of a mantissa followed by the
+ character "E", followed by an exponent. The mantissa MUST be a decimal number. The exponent
+ MUST be an integer. Leading zeroes and a preceding plus sign (<code>+</code>) are prohibited
+ in the exponent. If the exponent is zero, it must be indicated by <code>E0</code>.
+ For the mantissa, the preceding optional plus sign is prohibited and the decimal point is
+ required. Leading and trailing zeroes are prohibited subject to the following: number
+ representations must be normalized such that there is a single digit which is non-zero to the
+ left of the decimal point and at least a single digit to the right of the decimal point unless
+ the value being represented is zero. The canonical representation for zero is <code>0.0E0</code>.
+ <strong>xsd:double</strong>'s value space is defined by the IEEE double-precision 64-bit
+ floating point type [[!IEEE-754-1985]]; in JSON-LD the mantissa is rounded to 15 digits after the
+ decimal point.</p>
+
+ <p>To convert the number in JavaScript, implementers can use the following snippet of code:</p>
+
+ <pre class="example" data-transform="updateExample">
+ <!--
+ (value).toExponential(15).replace(/(\d)0*e\+?/,'$1E')
+ -->
+ </pre>
+
+ <p class="note">When data such as decimals need 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. Authors should instead use the expanded object form to
+ set the canonical lexical form directly.</p>
+
+ <p>The canonical lexical form of the <em>boolean</em> values <code>true</code> and <code>false</code>
+ are the strings <strong>true</strong> and <strong>false</strong>.</p>
+
+ <p>When JSON-native <tref>number</tref>s, are type coerced, lossless data round-tripping can not
+ be guaranted as rounding errors might occur. Additionally, only literals typed as
+ <strong>xsd:integer</strong>, <strong>xsd:double</strong>, and <strong>xsd:boolean</strong> are
+ automatically converted back to their JSON-native counterparts in when
+ <a href="#rdf-conversion">converting from RDF</a>.</p>
+
+ <p>Some JSON serializers, such as PHP's native implementation in some versions,
+ backslash-escape the forward slash character. For example, the value
+ <code>http://example.com/</code> would be serialized as <code>http:\/\/example.com\/</code>.
+ This is problematic as other JSON parsers might not understand those escaping characters.
+ There is no need to backslash-escape forward slashes in JSON-LD. To aid interoperability
+ between JSON-LD processors, a JSON-LD serializer MUST NOT backslash-escape forward slashes.</p>
+ </section>
+ </section>
+</section>
+
+<section>
+ <h2>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 JavaScript. If a JavaScript JSON-LD API is provided, the entirety
+ of the following API MUST be implemented.</p>
+
+ <section>
+ <h3>JsonLdProcessor</h3>
+
+ <p>The JSON-LD Processor interface is the high-level programming structure
+ that developers use to access the JSON-LD transformation methods.</p>
+
+ <p>It is important to highlight that conformant <tref title="JSON-LD Processor">JSON-LD processors</tref>
+ MUST NOT modify the input parameters.</p>
+
+ <dl title="[Constructor] interface JsonLdProcessor" class="idl">
+
+ <dt>void expand()</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>.
+
+ <dl class="parameters">
+ <dt>(object or object[] or DOMString) input</dt>
+ <dd>The JSON-LD object or array of JSON-LD objects to perform the expansion upon or an
+ <tref>IRI</tref> referencing the JSON-LD document to expand.</dd>
+ <dt>JsonLdCallback callback</dt>
+ <dd>A callback that is called when processing completed successfully
+ on the given <code>input</code>, or a fatal error prevented
+ processing from completing.</dd>
+ <dt>optional JsonLdOptions? options</dt>
+ <dd>A set of options to configure the used algorithms such. This allows, e.g.,
+ to set the input document's base <tref>IRI</tref>.</dd>
+ </dl>
+ </dd>
+
+ <dt>void compact()</dt>
+ <dd>
+ <a href="#compaction">Compacts</a> the given <code>input</code> using the
+ <code>context</code> according to the steps in the
+ <a href="#compaction-algorithm">Compaction Algorithm</a>.
+
+ <dl class="parameters">
+ <dt>(object or object[] or DOMString) input</dt>
+ <dd>The JSON-LD object or array of JSON-LD objects to perform the compaction upon or an
+ <tref>IRI</tref> referencing the JSON-LD document to compact.</dd>
+ <dt>(object or DOMString) context</dt>
+ <dd>The context to use when compacting the <code>input</code>; either in the
+ form of an <tref>JSON object</tref> or as <tref>IRI</tref>.</dd>
+ <dt>JsonLdCallback callback</dt>
+ <dd>A callback that is called when processing completed successfully
+ on the given <code>input</code>, or a fatal error prevented
+ processing from completing.</dd>
+ <dt>optional JsonLdOptions? options</dt>
+ <dd>A set of options to configure the used algorithms such. This allows, e.g.,
+ to set the input document's base <tref>IRI</tref>. This also includes
+ the <code>optimize</code> flag, which, if set, will allow processor-specific
+ optimization.</dd>
+ </dl>
+ </dd>
+
+ <dt>void flatten()</dt>
+ <dd>
+ <a href="#flattening">Flattens</a> the given <code>input</code> and
+ <a href="#compaction">compacts</a> it using the passed <code>context</code>
+ according to the steps in the <a href="#flattening-algorithm">Flattening Algorithm</a>.
+
+ <dl class="parameters">
+ <dt>(object or object[] or DOMString) input</dt>
+ <dd>The JSON-LD object or array of JSON-LD objects or an <tref>IRI</tref>
+ referencing the JSON-LD document to flatten.</dd>
+ <dt>(object or DOMString)? context</dt>
+ <dd>The context to use when compacting the flattened <code>input</code>; either
+ in the form of an <tref>JSON object</tref> or as <tref>IRI</tref>. If
+ <tref>null</tref> is passed, the result will not be compacted but keept
+ in expanded form.</dd>
+ <dt>JsonLdCallback callback</dt>
+ <dd>A callback that is called when processing completed successfully
+ on the given <code>input</code>, or a fatal error prevented
+ processing from completing.</dd>
+ <dt>optional JsonLdOptions? options</dt>
+ <dd>A set of options to configure the used algorithms such. This allows, e.g.,
+ to set the input document's base <tref>IRI</tref>.</dd>
+ </dl>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+ <h3>Callbacks</h3>
+
+ <p>JSON-LD processors utilize callbacks in order to return information in an
+ asynchronous manner to calling applications. This section details the
+ parameters sent to those callbacks.</p>
+
+ <section>
+ <h3>JsonLdCallback</h3>
+ <p>The <a>JsonLdCallback</a> is called when an API method
+ of <a>JsonLdProcessor</a> has completed successfully, detected an
+ issue, or been terminated by a fatal error.</p>
+
+ <dl title="callback JsonLdCallback = void" class="idl">
+ <dt>JsonLdProcessingIssue issue</dt>
+ <dd>If the value is <code>null</code>, then no issue was detected
+ during processing. If the value is non-<code>null</code>, a
+ processing issue was detected and the details will be contained
+ within the <code>issue</code> object.</dd>
+ <dt>object or object[] document</dt>
+ <dd>The output JSON-LD document at the time the issue was
+ detected.</dd>
+ </dl>
+ </section>
+ </section>
+
+ <section>
+ <h3>Data Structures</h3>
+ <p>This section describes datatype definitions used within the JSON-LD API.</p>
+
+ <section>
+ <h3>JsonLdOptions</h3>
+ <p>The <a>JsonLdOptions</a> type is used to pass various options to the <a>JsonLdProcessor</a> methods.</p>
+ <dl title="dictionary JsonLdOptions" class="idl">
+ <dt>DOMString base</dt>
+ <dd>The Base IRI to use when expanding the document. This overrides the value of
+ <em>input</em> if it is a <a>IRI</a>. If not specified and <em>input</em> is not
+ an <a>IRI</a>, the base IRI defaults to the current document IRI if in a browser context,
+ or the empty string if there is no document context.
+ </dd>
+ <dt>object or DOMString expandContext = null</dt>
+ <dd>A context that is used to initialize the active context when expanding a document.</dd>
+ <dt>boolean compactArrays = true</dt>
+ <dd>If set to <code>true</code>, the JSON-LD processor replaces arrays with just
+ one element with that element during compaction. If set to <code>false</code>,
+ all arrays will remain arrays even if they have just one element.
+ </dd>
+ <dt>JsonLdCallback issueCallback = null</dt>
+ <dd>If set to a function, the JSON-LD processor will use this callback
+ whenever it generates a warning, recoverable error, or fatal error
+ while processing the JSON-LD document. This callback is typically
+ used to convey debugging information regarding markup issues from the
+ JSON-LD processor to the developer. Note that this callback SHOULD be
+ used if a developer is interested in detecting issues while a
+ document is being processed as the <code>callback</code> parameter
+ provided to each API method is only used to report no errors or
+ fatal errors.
+ </dd>
+ <dt>boolean optimize = false</dt>
+ <dd>If set to <code>true</code>, the JSON-LD processor is allowed to
+ optimize the output of the <a href="#compaction-algorithm">Compaction Algorithm</a>
+ to produce even compacter representations. The algorithm for compaction
+ optimization is beyond the scope of this specification and thus
+ not defined. Consequently, different implementations MAY implement
+ different optimization algorithms.
+ </dd>
+ <dt>boolean useRdfType = false</dt>
+ <dd>If set to <code>true</code>, the JSON-LD processor will use the
+ expanded <code>rdf:type</code> IRI as the property instead of
+ <code>@type</code> when <a href="#convert-from-rdf-algorithm">converting from RDF</a>.
+ </dd>
+ <dt>boolean useNativeTypes = true</dt>
+ <dd>If set to <code>true</code>, the JSON-LD processor will try to convert
+ <tref title="typed value">typed values</tref> to JSON native types instead of using the
+ expanded object form when <a href="#convert-from-rdf-algorithm">converting from RDF</a>.
+ <code>xsd:boolean</code> values will be converted to <tref>true</tref> or <tref>false</tref>.
+ <code>xsd:integer</code> and <code>xsd:double</code> values will be
+ converted to
+ <tref title="number">JSON numbers</tref>.
+ </dd>
+ </dl>
+ </section>
+
+ <section>
+ <h3>JsonLdProcessingIssue</h3>
+
+ <p class="issue" data-number="153">Developers should note that the details of
+ processor issue handling are being actively debated.</p>
+
+ <p>The <a>JsonLdProcessingIssue</a> type is used to report processing
+ issues to a <a>JsonLdCallback</a>.</p>
+
+ <dl title="dictionary JsonLdProcessingIssue" class="idl">
+ <dt>JsonLdProcessorCode code</dt>
+ <dd>a string representing the particular issue type, as described in
+ the various algorithms in this document.</dd>
+ <dt>JsonLdProcessorIssueSeverity severity</dt>
+ <dd>a string representing the severity of the issue.</dd>
+ <dt>DOMString? message</dt>
+ <dd>an optional error message containing additional debugging information.
+ The specific contents of error messages are outside the scope of this
+ specification.</dd>
+ </dl>
+ </section>
+
+ <section>
+ <h3>JsonLdProcessorCode</h3>
+ <p>The JsonLdProcessorCode represent the collection of valid JSON-LD error
+ codes.</p>
+
+ <dl title="enum JsonLdProcessorCode" class="idl">
+ <dt>invalidSyntax</dt>
+ <dd>A violation of the grammar as defined by the JSON-LD syntax specification
+ [[!JSON-LD]] was detected.</dd>
+ <dt>retrievalFailure</dt>
+ <dd>There was a problem encountered loading a remote context.</dd>
+ <dt>listOfListsDetected</dt>
+ <dd>A list of lists was detected. List of lists are not supported in
+ this version of JSON-LD due to the algorithmic complexity associated
+ with conversion to RDF.</dd>
+ </dl>
+ </section>
+
+ <section>
+ <h3>JsonLdProcessorIssueSeverity</h3>
+ <p>The JsonLdProcessorIssueSeverity represents the collection of
+ valid JSON-LD processing severity codes.</p>
+
+ <dl title="enum JsonLdProcessorIssueSeverity" class="idl">
+ <dt>warning</dt>
+ <dd>A warning is used when the processor has detected markup that may
+ could negatively impact the final output of the processor. Warnings
+ MAY be used to convey alternate markup suggestions to the document
+ author.</dd>
+ <dt>recoverableError</dt>
+ <dd>A recoverable error is used when the processor detects markup
+ that violates rules outlined in the JSON-LD specifications, but
+ is able to recover from the error and continue processing.</dd>
+ <dt>fatalError</dt>
+ <dd>A fatal error is used when the processor detects markup
+ that violates rules outlined in the JSON-LD specifications and is
+ not able to recover from the error.</dd>
+ </dl>
+ </section>
+
+ </section>
+</section>
+
+<section class="appendix">
+ <h1>Acknowledgements</h1>
+
+ <p>A large amount of thanks goes out to the JSON-LD Community Group
+ participants who worked through many of the technical issues on the mailing
+ list and the weekly telecons - of special mention are Niklas Lindström,
+ François Daoust, Lin Clark, and Zdenko 'Denny' Vrandečić.
+ 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.
+ The work of Dave Lehn and Mike Johnson are appreciated for reviewing,
+ and performing several implementations of the specification. Ian Davis is
+ thanked for his work on RDF/JSON. Thanks also to Nathan Rixham,
+ Bradley P. Allen, Kingsley Idehen, Glenn McDonald, Alexandre Passant,
+ Danny Ayers, Ted Thibodeau Jr., Olivier Grisel, Josh Mandel, Eric Prud'hommeaux,
+ David Wood, Guus Schreiber, Pat Hayes, Sandro Hawke, and Richard Cyganiak
+ or their input on the specification.</p>
+</section>
+
+</body>
+</html>