--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/diffs/rdf-concepts-langstring.html Wed Nov 30 07:58:22 2011 -0800
@@ -0,0 +1,1267 @@
+<!DOCTYPE html>
+<html lang="en">
+ <head><style type="text/css"><!--
+
+.insert { background-color: #aaffaa }
+.delete { background-color: #ff8888; text-decoration: line-through }
+.tagInsert { background-color: #007700; color: #ffffff }
+.tagDelete { background-color: #770000; color: #ffffff }
+
+--></style>
+ <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+ <title>RDF 1.1 Concepts and Abstract Syntax</title>
+ <style type="text/css">
+.figure { font-weight: bold; text-align: center; }
+ </style>
+ <script src='../ReSpec.js/js/respec.js' class='remove'></script>
+ <script class='remove'>
+ var respecConfig = {
+ // specification status (e.g. WD, LCWD, NOTE, etc.). If in doubt use ED.
+ specStatus: "ED",
+
+ // the specification's short name, as in http://www.w3.org/TR/short-name/
+ shortName: "rdf11-concepts",
+
+ // if your specification has a subtitle that goes below the main
+ // formal title, define it here
+ // subtitle : "an excellent document",
+
+ // if you wish the publication date to be other than today, set this
+ // publishDate: "2009-08-06",
+
+ // if the specification's copyright date is a range of years, specify
+ // the start date here:
+ copyrightStart: "2004",
+
+ // if there is a previously published draft, uncomment this and set its YYYY-MM-DD date
+ // and its maturity status
+// previousPublishDate: "2004-02-10",
+// previousMaturity: "REC",
+
+ // if there a publicly available Editor's Draft, this is the link
+//@@@
+ edDraftURI: "http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html",
+
+ // if this is a LCWD, uncomment and set the end of its review period
+ // lcEnd: "2009-08-05",
+
+ // if there is an earler version of this specification at the Recommendation level,
+ // set this to the shortname of that version. This is optional and not usually
+ // necessary.
+ prevRecShortname: "rdf-concepts",
+
+ // if you want to have extra CSS, append them to this list
+ // it is recommended that the respec.css stylesheet be kept
+ extraCSS: ["http://dvcs.w3.org/hg/rdf/raw-file/default/ReSpec.js/css/respec.css"],
+
+ // editors, add as many as you like
+ // only "name" is required
+ editors: [
+ { name: "Richard Cyganiak", url: "http://richard.cyganiak.de/",
+ company: "DERI, NUI Galway", companyURL: "http://www.deri.ie/",
+ },
+// @@@ Details for David?
+ { name: "David Wood", // url: "http://example.org/",
+ company: "3 Round Stones", companyURL:
+ "http://www.3roundstones.com/",
+ },
+ ],
+ otherContributors: {
+ "Previous editor": [
+// @@@ Graham's affiliation has changed
+ { name: "Graham Klyne",
+ url: "http://www.ninebynine.org/",
+ company: "Nine by Nine",
+ //companyURL: "http://example.com/"
+ //mailto: "GK@NineByNine.org",
+ },
+// @@@ Jeremy's affiliation has changed
+ { name: "Jeremy J. Carroll",
+ //url: "http://www-uk.hpl.hp.com/people/jjc/",
+ company: "Hewlett Packard Labs",
+ //companyURL: "http://example.com/"
+ //mailto: "jjc@hpl.hp.com",
+ },
+// @@@ Brian's affiliation has changed
+ { name: "Brian McBride",
+ //url: "http://www-uk.hpl.hp.com/people/bwm/",
+ company: "Hewlett Packard Labs",
+ //companyURL: "http://example.com/"
+ //mailto: "bwm@hplb.hpl.hp.com",
+ note: "RDF 2004 Series Editor",
+ },
+ ],
+ },
+
+ // 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: "Your Name", url: "http://example.org/",
+ // company: "Your Company", companyURL: "http://example.com/" },
+ //],
+
+ // name of the WG
+ wg: "RDF Working Group",
+
+ // URI of the public WG page
+ wgURI: "http://www.w3.org/2011/rdf-wg/",
+
+ // name (with the @w3c.org) of the public mailing to which comments are due
+ wgPublicList: "public-rdf-comments",
+
+ // URI of the patent status for this WG, for Rec-track documents
+ // !!!! IMPORTANT !!!!
+ // This is important for Rec-track documents, do not copy a patent URI from a random
+ // document unless you know what you're doing. If in doubt ask your friendly neighbourhood
+ // Team Contact.
+ wgPatentURI: "http://www.w3.org/2004/01/pp-impl/46168/status",
+
+ // if this parameter is set to true, ReSpec.js will embed various RDFa attributes
+ // throughout the generated specification. The triples generated use vocabulary items
+ // from the dcterms, foaf, and bibo. The parameter defaults to false.
+ doRDFa: true,
+ };
+
+// @@@ A number of references have been patched into the local berjon.biblio and need to be added to the global biblio in CVS:
+ </script>
+ </head>
+
+ <body>
+
+<section id="abstract">
+ <p>The Resource Description Framework (RDF) is a framework for
+ representing information in the Web.</p>
+ <p>RDF Concepts and Abstract Syntax defines an abstract syntax
+ on which RDF is based, and which serves to link its concrete
+ syntax to its formal semantics. It also includes discussion of
+ key concepts, datatyping, character normalization
+ and handling of IRIs.</p>
+</section>
+
+
+<section id="section-Introduction">
+ <h2>Introduction</h2>
+
+ <p class="issue">This document reflects current progress of the RDF Working
+ Group towards updating the
+ <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/">2004
+ version of <em>RDF Concepts and Abstract Syntax</em></a>. The
+ editors expect to work on a number of issues, some of which are
+ listed in boxes like this throughout the document.</p>
+
+ <p>The Resource Description Framework (RDF) is a framework for
+ representing information in the Web.</p>
+
+ <p>This document defines an abstract syntax (a data model)
+ on which RDF is based,
+ and which serves to link concrete syntaxes to its formal
+ semantics. It also includes discussion of
+ key concepts, datatyping, character normalization
+ and handling of IRIs.</p>
+
+ <p>Normative documentation of RDF falls into the following
+ areas:</p>
+
+ <ul>
+ <li>Serialization syntaxes (Turtle [[TURTLE-TR]], RDFa [[RDFA-PRIMER]], RDF/XML [[RDF-SYNTAX-GRAMMAR]], N-Triples [[N-TRIPLES]]),</li>
+
+ <li>the RDF Vocabulary Description Language ([[RDF-SCHEMA]]),</li>
+
+ <li>a formal model-theoretic semantics [[!RDF-MT]], and</li>
+
+ <li>this document.</li>
+ </ul>
+
+ <p>The framework is designed so that vocabularies can be layered.
+ The terms defined in [[RDF-SCHEMA]] are the first such vocabulary.
+ Several other vocabularies for RDF are
+ mentioned in the Primer [[RDF-PRIMER]].</p>
+</section>
+
+
+<section id="conformance"></section>
+
+
+<section id="section-Concepts" class="informative">
+ <h2>RDF Concepts</h2>
+
+ <p class="issue">This section is quite redundant with later
+ normative sections and the RDF Primer. Its removal has been
+ proposed. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/issues/68">ISSUE-68</a>.</p>
+
+ <p>RDF uses the following key concepts:</p>
+
+ <ul>
+ <li>Graph data model</li>
+
+ <li>IRI-based vocabulary</li>
+
+ <li>Datatypes</li>
+
+ <li>Literals</li>
+
+ <li>Entailment</li>
+ </ul>
+
+
+<section id="section-data-model">
+ <h3>Graph Data Model</h3>
+
+ <p>The underlying structure of any expression in RDF is a
+ collection of triples, each consisting of a subject, a
+ predicate and an object. A set of such triples is called an RDF
+ graph (defined more formally in
+<a href="#section-Graph-syntax">section 6</a>). This can be
+ illustrated by a node and directed-arc diagram, in which each
+ triple is represented as a node-arc-node link (hence the term
+ “graph”).</p>
+
+ <div class="figure">
+ <img src="Graph-ex.gif" alt="image of the RDF triple comprising (subject, predicate, object)" />
+ </div>
+
+ <p>Each triple represents a statement of a relationship between
+ the things denoted by the nodes that it links. Each triple has
+ three parts:</p>
+ <ol>
+ <li>a <a>subject</a>,</li>
+ <li>an <a>object</a>, and</li>
+ <li>a <a>predicate</a> (also called a
+ <a>property</a>) that denotes a
+ relationship.</li>
+ </ol>
+ <p>The direction of the arc is significant: it always points
+ toward the object.</p>
+ <p>The <a title="node">nodes</a> of an RDF graph
+ are its subjects and objects.</p>
+ <p>The assertion of an RDF triple says that some relationship,
+ indicated by the predicate, holds between the things denoted by
+ subject and object of the triple. The assertion of an RDF graph
+ amounts to asserting all the triples in it, so the meaning of
+ an RDF graph is the conjunction (logical AND) of the statements
+ corresponding to all the triples it contains. A formal account
+ of the meaning of RDF graphs is given in [[!RDF-MT]].</p>
+</section>
+
+
+<section id="section-IRI-Vocabulary">
+ <h3>IRI-based Vocabulary and Node Identification</h3>
+
+ <p>A <a>node</a> may be an <a>IRI</a>, a <a>literal</a>,
+ or <a title="blank node">blank</a> (having no separate form of identification).
+ Properties are <a title="IRI">IRIs</a>.</p>
+ <p>An <a>IRI</a> or <a>literal</a> used as a node identifies what
+ that node represents. An IRI used as a predicate
+ identifies a relationship between the things represented by the nodes it connects. A
+ predicate IRI may also be a node in the graph.</p>
+ <p>A <a>blank node</a> is a node that is
+ not an IRI or a literal. In the RDF abstract syntax, a
+ blank node is just a unique node that can be used in one or
+ more RDF statements.</p>
+ <p>A convention used by some linear representations of an RDF
+ graph to allow several statements to use the same
+ blank node is to use a <dfn>blank node
+ identifier</dfn>, which is a local identifier that can be
+ distinguished from all IRIs and literals. When graphs are
+ merged, their blank nodes must be kept distinct if meaning is
+ to be preserved; this may call for re-allocation of blank node
+ identifiers. Note that such blank node identifiers are not part
+ of the RDF abstract syntax, and the representation of triples
+ containing blank nodes is entirely dependent on the particular
+ concrete syntax used.</p>
+</section>
+
+
+<section id="section-Datatypes-intro">
+ <h3>Datatypes</h3>
+
+ <p>Datatypes are used by RDF in the representation of values such
+ as integers, floating point numbers and dates.</p>
+
+ <p>
+A datatype consists of a lexical space, a value space and a lexical-to-value
+mapping, see <a href="#section-Datatypes">section 5</a>.
+</p>
+
+ <p>For example, the lexical-to-value mapping for the XML Schema datatype
+ <var>xsd:boolean</var>, where each member of the value space
+ (represented here as 'T' and 'F') has two lexical representations,
+ is as follows:</p>
+
+ <table border="1" cellpadding="5" summary=
+ "A table detailing the xsd:boolean datatype.">
+ <tr>
+ <th align="left">Value Space</th>
+
+ <td>{T, F}</td>
+ </tr>
+
+ <tr>
+ <th align="left">Lexical Space</th>
+
+ <td>{"0", "1", "true", "false"}</td>
+ </tr>
+
+ <tr>
+ <th align="left">Lexical-to-Value Mapping</th>
+
+ <td>{<"true", T>, <"1", T>, <"0", F>,
+ <"false", F>}</td>
+ </tr>
+ </table>
+
+ <p>RDF predefines just one datatype <code><a>rdf:XMLLiteral</a></code>,
+ used for
+ embedding XML in RDF (see <a href="#section-XMLLiteral">section
+ 5.1</a>).<span class="insert"> RDF also defines
+ </span><code><a title="language-tagged string"><span class="insert">rdf:langString</span></a></code><span class="insert">, used
+ for plain text in a natural language, but this is not formally considered
+ a datatype.</span></p>
+
+ <p>There is no built-in concept of numbers or dates or other common
+ values. Rather, RDF defers to datatypes that are defined
+ separately, and identified with <a title="IRI">IRIs</a>.
+ The predefined XML Schema
+ datatypes [[!XMLSCHEMA-2]] are expected
+ to be widely used for this purpose.</p>
+
+
+ <p>RDF provides no mechanism for defining new datatypes. XML Schema
+ Datatypes [[!XMLSCHEMA-2]] provides an
+ extensibility framework suitable for defining new datatypes for use
+ in RDF.</p>
+</section>
+
+
+<section id="section-Literals">
+ <h3>Literals</h3>
+
+ <p><a title="literal">Literals</a> are used to identify values such as numbers and dates
+ by means of a lexical representation. Anything represented by a
+ literal could also be represented by an <a>IRI</a>, but it is often more
+ convenient or intuitive to use literals.<span class="insert"> All literals have a
+ </span><a><span class="insert">datatype IRI</span></a><span class="insert">. A literal denotes a member of the
+ datatype's </span><a><span class="insert">value space</span></a><span class="insert">, as indicated by its
+ </span><a><span class="insert">lexical-to-value mapping</span></a><span class="insert">.</span></li>
+
+ <p>A literal may be the object of an RDF statement, but not the
+ subject or the predicate.</p>
+
+ <p><span class="delete">Literals may be </span><span class="delete">typed</span><span class="delete"> or </span><span class="delete">language-tagged</span><span class="delete">:</span>
+
+
+ <span class="delete">A </span><span class="delete">typed literal</span><span class="delete"> is a string combined with a
+ </span><span class="delete">datatype IRI</span><span class="delete">. It denotes the
+ member of the identified datatype's value space obtained by
+ applying the lexical-to-value mapping to the literal string.</span>
+
+ <span class="delete">A </span><span class="delete">language-tagged literal</span><span class="delete"> is a string combined
+ with a language tag. This may be used for
+ plain text in a natural language. Language-tagged literals
+ are self-denoting.</span>
+
+
+ Continuing the example from <a href="#section-Datatypes-intro">section
+ 3.3</a>, the<span class="delete"> typed</span> literals that can be defined using the XML
+ Schema datatype <var>xsd:boolean</var> are:</p>
+
+ <table border="1" cellpadding="5" summary=
+ "This table lists the literals of type xsd:boolean.">
+ <tr>
+ <th><span class="delete">Typed </span>Literal</th>
+
+ <th>Lexical-to-Value Mapping</th>
+
+ <th>Value</th>
+ </tr>
+
+ <tr>
+ <td align="center"><xsd:boolean, "true"></td>
+
+ <td align="center"><"true", T></td>
+
+ <td align="center">T</td>
+ </tr>
+
+ <tr>
+ <td align="center"><xsd:boolean, "1"></td>
+
+ <td align="center"><"1", T></td>
+
+ <td align="center">T</td>
+ </tr>
+
+ <tr>
+ <td align="center"><xsd:boolean, "false"></td>
+
+ <td align="center"><"false", F></td>
+
+ <td align="center">F</td>
+ </tr>
+
+ <tr>
+ <td align="center"><xsd:boolean, "0"></td>
+
+ <td align="center"><"0", F></td>
+
+ <td align="center">F</td>
+ </tr>
+ </table>
+
+ <p>For text that may contain
+ markup, use <span class="delete">typed </span>literals
+with type <a href="#section-XMLLiteral">rdf:XMLLiteral</a>.
+If language annotation is required,
+it must be explicitly included as markup, usually by means of an
+<code>xml:lang</code> attribute.
+XHTML [[XHTML10]] may be included within RDF
+in this way. Sometimes, in this latter case,
+ an additional <code>span</code> or <code>div</code>
+ element is needed to carry an
+<code>xml:lang</code> or <code>lang</code> attribute.
+ </p>
+
+<p class="issue">Update the XHTML 1.0 reference to something more recent?
+
+<span class="delete">
+The string in both plain and typed literals is recommended to
+be in Unicode Normal Form C [[!NFC]]. This is motivated
+by [[CHARMOD]] particularly
+</span><span class="delete">section 4
+Early Uniform Normalization</span><span class="delete">.
+</span></p>
+
+</section>
+
+
+<section id="section-Entailment">
+ <h3>Entailment</h3>
+
+ <p>The ideas on meaning and inference in RDF are underpinned by the
+ formal concept of <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#entail">
+<cite>entailment</cite></a>, as
+ discussed in the RDF
+ semantics document [[!RDF-MT]].
+In brief, an RDF expression A is said to
+<dfn title="entailment">entail</dfn> another RDF expression B
+if every possible
+arrangement of things in the world that makes A true also makes B
+true. On this basis, if the truth of A is presumed or demonstrated
+then the truth of B can be inferred .
+</p>
+</section>
+
+</section>
+
+
+<section id="section-URIspaces">
+ <h2>RDF Vocabulary IRI and Namespace</h2>
+
+ <p>RDF uses <a title="IRI">IRIs</a> to identify resources
+ and properties. Certain
+ IRIs with the following leading substring are defined by the
+ RDF specifications to denote specific concepts:</p>
+
+ <ul>
+ <li><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>
+ (conventionally associated with namespace prefix <code>rdf:</code>)</li>
+ </ul>
+
+ <p>Vocabulary terms in the <code>rdf:</code>
+ namespace are listed and described in detail in the
+ RDF Schema specification [[!RDF-SCHEMA]].</p>
+
+ <p class="note">The RDF namespace is also used as an
+ XML namespace [[XML-NAMES]] to define a number of additional
+ element and attribute names for purely syntactic purposes within
+ the RDF/XML syntax ([[RDF-SYNTAX-GRAMMAR]],
+ <a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#section-Namespace">section 5.1</a>).
+ These terms (e.g., <code>rdf:about</code> and <code>rdf:ID</code>)
+ do not denote concepts.</p>
+</section>
+
+
+<section id="section-Datatypes">
+ <h2>Datatypes</h2>
+
+ <p class="issue">This section perhaps should discuss
+ <a href="http://www.w3.org/TR/rdf-mt/#dtype_interp">the XSD datatype map</a>
+ and <code><a href="http://www.w3.org/TR/rdf-plain-literal/">rdf:PlainLiteral</a></code>.
+ This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/70">ISSUE-70</a>.</p>
+
+<p>
+The datatype abstraction used in RDF is compatible with
+the abstraction used in
+XML Schema Part 2:
+ Datatypes [[!XMLSCHEMA-2]].</p>
+
+
+ <p>
+A <dfn>datatype</dfn> consists of a lexical space, a value space
+ and a lexical-to-value
+ mapping.
+</p>
+
+
+<p>The <dfn>lexical space</dfn> of a datatype is a set of Unicode [[!UNICODE]] strings.</p>
+<p>
+The <dfn>lexical-to-value mapping</dfn> of a datatype is a set of pairs whose
+first element belongs to
+the <a>lexical space</a> of the datatype,
+and the second element belongs to the
+ <dfn>value space</dfn> of the datatype:
+</p>
+<ul>
+<li>
+Each member of the lexical space is paired with (maps to) exactly one member
+of the value space.
+</li>
+<li>
+Each member of the value space may be paired with any number (including
+zero) of members of the lexical space (lexical representations for that
+value).
+</li>
+</ul>
+<p>
+A datatype is identified by one or more IRIs.
+</p>
+<p>
+RDF may be used with any datatype definition that conforms to this
+abstraction, even if not defined in terms of XML Schema.
+</p>
+ <p>Certain XML Schema built-in datatypes are not suitable for use
+ within RDF. For example, the
+<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#QName">QName</a>
+datatype requires a namespace declaration to be in scope during
+ the mapping, and is not recommended for use in RDF.
+ [[!RDF-MT]] contains a
+<a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#dtype_interp">more detailed discussion</a>
+ of specific XML Schema built-in datatypes. </p>
+
+<div class="note">
+<p>When the datatype is defined using XML Schema:
+</p>
+<ul>
+<li>
+All values correspond to some lexical form, either using
+the lexical-to-value mapping of the datatype or if it is a union
+datatype with a lexical mapping associated with one of the member
+datatypes.
+</li>
+<li>
+XML Schema facets remain part of the datatype and are used by the XML
+Schema mechanisms that control the lexical space and the value space;
+however, RDF does not define a standard mechanism to access these facets.</li>
+
+<li>In [[XMLSCHEMA-1]],
+<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#section-White-Space-Normalization-during-Validation">
+white space normalization</a> occurs
+during
+<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#key-vn">validation</a>
+according to the value of the
+<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#rf-whiteSpace">whiteSpace
+facet</a>. The lexical-to-value mapping used in RDF datatyping
+occurs after this, so that the whiteSpace facet has no
+effect in RDF datatyping.
+</li>
+</ul>
+
+</div>
+
+ <p class="note"><a title="language-tagged string"><span class="insert">Language-tagged
+ strings</span></a><span class="insert"> have the </span><a><span class="insert">datatype IRI</span></a>
+ <code><span class="insert">http://www.w3.org/1999/02/22-rdf-syntax-ns#langString</span></code><span class="insert">.
+ No datatype is formally defined for this IRI because the definition
+ of datatypes does not accommodate </span><a title="language tag"><span class="insert">language tags</span></a><span class="insert">.
+ The </span><a><span class="insert">value space</span></a><span class="insert"> associated with the datatype IRI is the set
+ of all pairs of strings and language tags.</span></p>
+
+
+<section id="section-XMLLiteral">
+ <h3>XML Content within an RDF Graph</h3>
+
+ <p class="issue">The canonicalization rules required for XML literals
+ are quite complicated. Increasingly, RDF is produced and consumed in
+ environments where no XML parser and canonicalization engine is
+ available. A possible change to relax the requirements for the
+ lexical space, while retaining the value space, is under discussion.
+ This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/13">ISSUE-13</a>.</p>
+
+ <p>RDF provides for XML content as a possible literal value.
+ Such content is indicated in an RDF graph using a <span class="delete">typed </span>literal
+ whose datatype is <span class="delete">a special</span><span class="insert">the</span> built-in datatype
+ <dfn>rdf:XMLLiteral</dfn>,
+ defined as follows.</p>
+
+
+ <dl>
+ <dt><a name="XMLLiteral-uri" id="XMLLiteral-uri">An IRI for
+identifying this datatype</a></dt>
+
+ <dd>is
+ <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>.</dd>
+
+
+
+
+ <dt><a name="XMLLiteral-lexical-space" id="XMLLiteral-lexical-space">The lexical space</a></dt>
+
+<dd>is the set of all
+strings:
+<ul>
+<li>which are well-balanced, self-contained
+<a href="http://www.w3.org/TR/2000/REC-xml-20001006#NT-content">
+XML content</a>
+[[!XML10]];
+</li>
+<li>for which encoding as UTF-8
+[[!UTF-8]] yields
+<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-exclusive-canonical-XML">
+exclusive
+Canonical XML </a> (with comments, with empty
+<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-InclusiveNamespaces-PrefixList">
+InclusiveNamespaces PrefixList
+</a>) [[!XML-EXC-C14N]];
+</li>
+<li>for which embedding between an arbitrary XML start tag and an end tag
+yields a document conforming to <a href=
+ "http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
+ Namespaces</a> [[!XML-NAMES]]</li>
+</ul>
+</dd>
+
+
+ <dt><a name="XMLLiteral-value-space" id="XMLLiteral-value-space">The value space</a></dt>
+
+ <dd>is a set of entities, called XML values, which is:
+<ul>
+<li>disjoint from the lexical space;</li>
+<li>disjoint from the value space of any other datatype that is not explicitly defined as a sub- or supertype of this datatype;</li>
+<li>disjoint from the set of Unicode character strings [[!UNICODE]];</li>
+<li>and in 1:1 correspondence with the lexical space.</li>
+</ul>
+</dd>
+
+ <dt><a name="XMLLiteral-mapping" id="XMLLiteral-mapping">The lexical-to-value mapping</a></dt>
+
+ <dd>
+is a one-one mapping from the lexical space onto the value space,
+ i.e. it is both injective and surjective.
+</dd>
+
+
+
+ </dl>
+
+ <p class="note">Not all values of this datatype are compliant
+ with XML 1.1 [[XML11]]. If compliance
+ with XML 1.1 is desired, then only those values that are
+<a href="http://www.w3.org/TR/2002/CR-xml11-20021015/#sec2.13">fully
+ normalized</a> according to XML 1.1 should be used.</p>
+
+ <p class="note">XML values can be thought of as the
+[[XML-INFOSET]] or the [[XPATH]]
+nodeset corresponding to the lexical form, with an appropriate equality
+function.</p>
+
+ <p class="note">RDF applications may use additional equivalence relations, such as
+that which relates an
+<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#string"><code>xsd:string</code></a>
+
+with an <code>rdf:XMLLiteral</code> corresponding to
+a single text node of the same string.</p>
+
+</section>
+
+</section>
+
+
+<section id="section-Graph-syntax">
+ <h2>Abstract Syntax</h2>
+
+ <p>This section defines the RDF abstract syntax. The RDF abstract
+ syntax is a set of triples, called the RDF graph.</p>
+
+ <p>This section also defines equivalence between RDF graphs. A
+ definition of equivalence is needed to support the RDF Test Cases
+ [[RDF-TESTCASES]] specification.</p>
+
+<p class="note">This <em>abstract</em> syntax is the
+syntax over which the formal semantics are defined.
+Implementations are free to represent RDF graphs in
+any other equivalent form. As an example:
+in an RDF graph,
+literals with datatype <tt>rdf:XMLLiteral</tt> can be represented
+in a non-canonical
+format, and canonicalization performed during the comparison between two
+such literals. In this example the comparisons may be
+being performed either between syntactic structures or
+between their denotations in the domain of discourse.
+Implementations that do not require any such comparisons can
+hence be optimized.
+</p>
+
+
+<section id="section-triples">
+ <h3>RDF Triples</h3>
+
+ <p>An <dfn>RDF triple</dfn> contains three components:</p>
+
+ <ul>
+ <li>the <dfn>subject</dfn>, which is an
+ <a>IRI</a> or a <a>blank node</a></li>
+
+ <li>the <dfn>predicate</dfn>, which is an <a>IRI</a></li>
+
+ <li>the <dfn>object</dfn>, which is an <a>IRI</a>,
+ a <a>literal</a> or a <a>blank node</a></li>
+ </ul>
+
+ <p>An RDF triple is conventionally written in the order subject,
+ predicate, object.</p>
+
+ <p>The predicate is also known as the <dfn>property</dfn> of the triple.</p>
+
+ <p><a title="IRI">IRIs</a>, <a title="blank node">blank nodes</a> and
+ <a title="literal">literals</a> are collectively known as
+ <dfn title="RDF term">RDF terms</dfn>.</p>
+</section>
+
+
+<section id="section-rdf-graph">
+ <h3>RDF Graph</h3>
+
+ <p>An <dfn>RDF graph</dfn> is a set of RDF triples.</p>
+
+ <p>The set of <dfn title="node">nodes</dfn> of an RDF graph is the set of subjects and objects of
+ triples in the graph.</p>
+</section>
+
+
+<section id="section-graph-equality">
+ <h3>Graph Equivalence</h3>
+
+ <p>Two <a title="RDF graph">RDF graphs</a> <var>G</var> and <var>G'</var> are equivalent if there
+ is a bijection <var>M</var> between the sets of nodes of the two graphs,
+ such that:</p>
+
+ <ol>
+ <li><var>M</var> maps blank nodes to blank nodes.</li>
+ <li><var>M(lit)=lit</var> for all <a title="literal">RDF literals</a> <var>lit</var> which
+ are nodes of <var>G</var>.</li>
+
+ <li><var>M(uri)=uri</var> for all <a title="IRI">IRIs</a> <var>uri</var>
+ which are nodes of <var>G</var>.</li>
+
+ <li>The triple <var>( s, p, o )</var> is in <var>G</var> if and
+ only if the triple <var>( M(s), p, M(o) )</var> is in
+ <var>G'</var></li>
+ </ol>
+ <p>With this definition, <var>M</var> shows how each blank node
+ in <var>G</var> can be replaced with
+ a new blank node to give <var>G'</var>.</p>
+</section>
+
+
+<section id="section-IRIs">
+ <h3>IRIs</h3>
+
+ <p>An <dfn title="IRI"><acronym title="Internationalized Resource Identifier">IRI</acronym></dfn>
+ (Internationalized Resource Identifier) within an RDF graph
+ is a Unicode string [[!UNICODE]] that conforms to the syntax
+ defined in RFC 3987 [[!IRI]]. IRIs are a generalization of
+ <dfn title="URI"><acronym title="Uniform Resource Identifier">URI</acronym>s</dfn>
+ [[URI]]. Every absolute URI and URL is an IRI.</p>
+
+ <p>IRIs in the RDF abstract syntax MUST be absolute, and MAY
+ contain a fragment identifier.</p>
+
+ <p>Two IRIs are equal if and only if they are equivalent
+ under Simple String Comparison according to
+ <a href="http://tools.ietf.org/html/rfc3987#section-5.1">section 5.1</a>
+ of [[!IRI]]. Further normalization MUST NOT be performed when
+ comparing IRIs for equality.</p>
+
+ <p class="note">When IRIs are used in operations that are only
+ defined for URIs, they must first be converted according to
+ the mapping defined in
+ <a href="http://tools.ietf.org/html/rfc3987#section-3.1">section 3.1</a>
+ of [[!IRI]]. A notable example is retrieval over the HTTP
+ protocol. The mapping involves UTF-8 encoding of non-ASCII
+ characters, %-encoding of octets not allowed in URIs, and
+ Punycode-encoding of domain names.</p>
+
+ <p class="note">Some concrete syntaxes permit relative IRIs
+ as a shorthand for absolute IRIs, and define how to resolve
+ the relative IRIs against a base IRI.</p>
+
+ <p class="note">Previous versions of RDF used the term
+ “<dfn>RDF URI Reference</dfn>” instead of “IRI” and allowed
+ additional characters:
+ “<code><</code>”, “<code>></code>”,
+ “<code>{</code>”, “<code>}</code>”,
+ “<code>|</code>”, “<code>\</code>”,
+ “<code>^</code>”, “<code>`</code>”,
+ ‘<code>“</code>’ (double quote), and “<code> </code>” (space).
+ In IRIs, these characters must be percent-encoded as
+ described in <a href="http://tools.ietf.org/html/rfc3986#section-2.1">section 2.1</a>
+ of [[URI]].</p>
+
+ <div class="note">
+ <p>Interoperability problems can be avoided by minting
+ only IRIs that are normalized according to
+ <a href="http://tools.ietf.org/html/rfc3987#section-5">Section 5</a>
+ of [[!IRI]]. Non-normalized forms that should be avoided
+ include:</p>
+
+ <ul>
+ <li>Uppercase characters in scheme names and domain names</li>
+ <li>Percent-encoding of characters where it is not
+ required by IRI syntax</li>
+ <li>Explicitly stated HTTP default port
+ (<code>http://example.com:80/</code>);
+ <code>http://example.com/</code> is preferrable</li>
+ <li>Completely empty path in HTTP IRIs
+ (<code>http://example.com</code>);
+ <code>http://example.com/</code> is preferrable</li>
+ <li>“<code>/./</code>” or “<code>/../</code>” in the path
+ component of an IRI</li>
+ <li>Lowercase hexadecimal letters within percent-encoding
+ triplets (“<code>%3F</code>” is preferable over
+ “<code>%3f</code>”)</li>
+ <li>Punycode-encoding of Internationalized Domain Names
+ in IRIs</li>
+ <li>IRIs that are not in Unicode Normalization
+ Form C [[!NFC]]</li>
+ </ul>
+ </div>
+</section>
+
+
+<section id="section-Graph-Literal">
+ <h3>RDF Literals</h3>
+
+ <span class="delete">This section is a major departure from RDF 2004
+ as </span><span class="delete">simple literals</span><span class="delete"> are now treated
+ as syntactic sugar for </span><span class="delete">xsd:string</span>
+ <span class="delete">typed literals</span><p><span class="insert">A </span><dfn><span class="insert">literal</span></dfn><span class="insert"> in an </span><a><span class="insert">RDF graph</span></a><span class="insert"> consists of:</span></p>
+
+ <ul>
+ <li><span class="insert">a </span><dfn><span class="insert">lexical form</span></dfn><span class="insert"> being a Unicode [[!UNICODE]] string,
+ which should be in Normal Form C [[!NFC]],</span></li>
+ <li><span class="insert">a </span><dfn><span class="insert">datatype IRI</span></dfn><span class="insert"> being an </span><a><span class="insert">IRI</span></a>.<span class="delete"> Further changes
+ to RDF's literal design are under consideration:
+ </span><span class="delete">Language-tagged literals</span><span class="delete">
+ may receive a datatype, and
+ </span><span class="delete">rdf:PlainLiteral</span><span class="delete">s</span><span class="delete"> [[RDF-PLAINLITERAL]]
+ may be folded into the design somehow. This is
+ </span><span class="delete">ISSUE-71</span><span class="delete">.</span></li>
+ </ul>
+
+ <p>A <dfn><span class="insert">language-tagged string</span></dfn><span class="insert"> is any </span><a>literal<span class="delete"> in an</span></a><span class="insert">
+ whose</span> <a><span class="delete">RDF graph</span><span class="delete"> is either a
+ </span><span class="insert">datatype IRI</span></a><span class="insert"> is equal to
+ </span><code><span class="insert">http://www.w3.org/1999/02/22-rdf-syntax-ns#langString</span></code><span class="insert">.
+ In addition to </span><a><span class="delete">typed literal</span><span class="delete"> or a </span><span class="insert">lexical form</span></a><span class="insert"> and datatype IRI,
+ a </span>language-tagged <span class="delete">literal</span><span class="delete">.</span><span class="insert">string also has:</span></p>
+
+ <span class="delete">All literals have a </span><span class="delete">lexical form</span><span class="delete"> being a Unicode
+ [[!UNICODE]] string, which SHOULD be in Normal Form C [[!NFC]].</span>
+
+ <span class="delete">Language-tagged literals</span><span class="delete"> have
+ a </span><span class="delete">lexical form</span><span class="delete"> and </span><ul>
+ <li>a non-empty <dfn>language tag</dfn> as
+ defined by [[!BCP47]].
+ The language tag MUST be well-formed according to
+ <a href="http://tools.ietf.org/html/bcp47#section-2.2.9">section 2.2.9</a>
+ of [[!BCP47]], and MUST be normalized to lowercase.</li>
+ </ul>
+
+ <span class="delete">Typed literals</span><span class="delete"> have a </span><span class="delete">lexical form</span><span class="delete">
+ and a </span><span class="delete">datatype IRI</span><span class="delete"> being an </span><span class="delete">IRI</span><span class="delete">.</span>
+
+ <p>Concrete syntaxes MAY support <dfn title="simple literal">simple
+ literals</dfn>, consisting of only a <a>lexical form</a>
+ without any <span class="insert">datatype IRI or </span>language <span class="delete">tag or </span><span class="insert">tag. Simple literals only
+ exist in concrete syntaxes, and are treated as
+ syntactic sugar for abstract syntax
+ </span><a title="literal"><span class="insert">literals</span></a><span class="insert"> with the </span><a>datatype <span class="delete">IRI. Simple literals only
+ exist in concrete syntaxes, and are treated as
+ syntactic sugar for abstract syntax
+ </span><span class="delete">typed literals</span><span class="delete"> with the datatype </span>IRI</a>
+ <code>http://www.w3.org/2001/XMLSchema#string</code>.
+ </p>
+
+ <p class="note"><span class="insert">In earlier versions of RDF, literals with a
+ </span><a><span class="insert">language tag</span></a><span class="insert"> did not have a </span><a><span class="insert">datatype IRI</span></a><span class="insert">, and
+ </span><a title="simple literal"><span class="insert">simple literals</span></a><span class="insert"> could appear
+ directly in the abstract syntax. </span>Simple literals and <span class="delete">language-tagged </span>literals<span class="delete"> are
+ </span><span class="insert"> with a
+ language tag were </span>collectively known as <dfn>plain literals</dfn>.
+
+ <span class="delete">Earlier versions of RDF allowed
+ </span><span class="delete">simple literals</span><span class="delete"> in the abstract syntax.</span></p>
+
+ <p class="note">Literals in which the lexical form begins with a
+ composing character (as defined by [[CHARMOD]]) are allowed however they may cause
+ interoperability problems, particularly with XML version 1.1 [[XML11]].</p>
+
+ <p class="note">Earlier versions of RDF permitted tags that
+ adhered to the generic tag/subtag syntax of language tags,
+ but were not well-formed according to [[!BCP47]]. Such
+ language tags do not conform to RDF 1.1.</p>
+
+ <p class="note">When using the language tag, care must be
+ taken not to confuse language with locale. The language
+ tag relates only to human language text. Presentational
+ issues should
+ be addressed in end-user applications.</p>
+
+ <p class="note">The case normalization of
+language tags is part of
+ the description of the abstract syntax, and consequently the abstract
+ behaviour of RDF applications. It does not constrain an
+ RDF implementation to actually normalize the case. Crucially, the result
+ of comparing two language tags should not be sensitive to the case of
+ the original input.</p>
+
+
+<section id="section-Literal-Equality">
+ <h4>Literal Equality</h4>
+
+ <p>Two literals are equal if and only if all of the following
+ hold:</p>
+
+ <ul>
+ <li>The strings of the two lexical forms compare equal, character
+ by character.</li>
+
+ <li>Either both or neither have language tags.</li>
+
+ <li>The language tags, if any, compare
+ equal.</li>
+
+ <li>Either both or neither have datatype IRIs.</li>
+
+ <li>The two datatype IRIs, if any, compare equal, character by
+ character.</li>
+ </ul>
+
+
+
+ <p class="note">RDF Literals are distinct and distinguishable
+
+ from <a title="IRI">IRIs</a>; e.g. <code>http://example.org/</code>
+ as <span class="delete">an RDF
+ Literal (untyped, without a language tag)</span><span class="insert">a string </span><a><span class="insert">literal</span></a> is not equal to
+ <code>http://example.org/</code>
+ as an IRI.</p>
+</section>
+
+
+<section id="section-Literal-Value">
+ <h4>The Value Corresponding to a<span class="delete"> Typed</span> Literal</h4>
+
+ <p>The <a>datatype IRI</a> refers to a <a>datatype</a>. For XML Schema
+
+ <a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#built-in-datatypes">built-in</a>
+ datatypes, IRIs such as
+ <code>http://www.w3.org/2001/XMLSchema#int</code> are used. The IRI
+ of the datatype <a href="#section-XMLLiteral"><tt>rdf:XMLLiteral</tt></a> may be used.
+ There may be other, implementation dependent, mechanisms by which
+ IRIs refer to datatypes.</p>
+
+ <p>The <dfn><span class="insert">literal </span>value</dfn> associated with a <span class="delete">typed </span><a>literal<span class="delete"> is found by
+ </span></a><span class="insert"> is:</span></p>
+
+ <ul>
+ <li><strong><span class="insert">If the literal is a </span><a><span class="insert">language-tagged string</span></a><span class="insert">:</span></strong><span class="insert">
+ a pair consisting of its </span><a><span class="insert">lexical form</span></a><span class="insert"> and its </span><a><span class="insert">language tag</span></a><span class="insert">,
+ in that order.</span></li>
+ <li><strong><span class="insert">Otherwise:</span></strong><span class="insert"> the result of </span>applying the
+ <a>lexical-to-value mapping</a> associated with the <a>datatype IRI </a>
+ to<span class="delete">
+ the </span><span class="insert"> the </span><a>lexical <span class="delete">form.
+ </span><span class="insert">form</span></a><span class="insert">.</span></li>
+ </ul>
+
+ <p>
+ If the lexical form is not in
+ the lexical space of the datatype associated with the datatype IRI,
+then no literal value can be associated with the<span class="delete"> typed</span> literal.
+Such a case, while in error, is not <em>syntactically</em> ill-formed.</p>
+
+
+
+
+
+
+ <p class="note">
+In application contexts, comparing the values of<span class="delete"> typed</span> literals (see
+<a href="#section-Literal-Value">
+section
+6.5.2</a>)
+is usually more helpful than comparing their syntactic forms (see
+<a href="#section-Literal-Equality">
+section
+6.5.1</a>).
+Similarly, for comparing RDF Graphs,
+semantic notions of entailment (see
+[[!RDF-MT]]) are usually
+more helpful than syntactic equality (see
+<a href="#section-graph-equality">
+section
+6.3</a>).</p>
+
+</section>
+
+</section>
+
+
+<section id="section-blank-nodes">
+ <h3>Blank Nodes</h3>
+
+<p>
+The <dfn title="blank node">blank nodes</dfn> in an RDF graph
+are drawn from an infinite set.
+This set of blank nodes, the set of all <a title="IRI">IRIs</a>
+and the set of all <a title="literal">literals</a> are pairwise disjoint.
+</p>
+<p>
+Otherwise, this set of blank nodes is arbitrary.
+</p>
+<p>RDF makes no reference to any internal structure of blank nodes.
+Given two blank nodes, it is
+possible to determine whether or not they are the same.</p>
+
+
+<section id="section-skolemization">
+ <h4>Replacing Blank Nodes with IRIs</h4>
+
+ <p>Blank nodes do not have identifiers in the RDF abstract syntax. The
+ <a title="blank node identifier">blank node identifiers</a> introduced
+ by some concrete syntaxes have only
+ local scope and are purely an artifact of the serialization.</p>
+
+ <p>In situations where stronger identification is needed, systems MAY
+ systematically transform some or all of the blank nodes in an RDF graph
+ into IRIs [[!IRI]]. Systems wishing to do this SHOULD mint a new, globally
+ unique IRI (a <dfn>Skolem IRI</dfn>) for each blank node so transformed.</p>
+
+ <p>This transformation does not change the meaning of an RDF graph,
+ provided that the Skolem IRIs do not occur anywhere else.</p>
+
+ <p>Systems may wish to mint Skolem IRIs in such a way that they can
+ recognize the IRIs as having been introduced solely to replace a blank
+ node, and map back to the source blank node where possible.</p>
+
+ <p>Systems that want Skolem IRIs to be recognizable outside of the system
+ boundaries SHOULD use a well-known IRI [[WELL-KNOWN]] with the registered
+ name <code>genid</code>. This is an IRI that uses the HTTP or HTTPS scheme,
+ or another scheme that has been specified to use well-known IRIs; and whose
+ path component starts with <code>/.well-known/genid/</code>.
+
+ <p>For example, the authority responsible for the domain
+ <code>example.com</code> could mint the following recognizable Skolem IRI:</p>
+
+ <pre>http://example.com/.well-known/genid/d26a2d0e98334696f4ad70a677abc1f6</pre>
+
+ <p class="issue">IETF registration of the <code>genid</code> name is
+ currently in progress.</p>
+
+ <p class="note">RFC 5785 [[WELL-KNOWN]] only specifies well-known URIs,
+ not IRIs. For the purpose of this document, a well-known IRI is any
+ IRI that results in a well-known URI after IRI-to-URI mapping [[!IRI]].</p>
+</section>
+
+</section>
+
+
+<section id="section-multigraph">
+ <h2>Abstract Syntax for Working with Multiple Graphs</h2>
+
+ <div class="issue">
+ <p>The Working Group will standardize a model and semantics for
+ multiple graphs and graphs stores. The
+ <a href="http://www.w3.org/2011/01/rdf-wg-charter">charter</a> notes:</p>
+
+ <blockquote>The RDF Community has used the
+ term “named graphs” for a number of years in various settings,
+ but this term is ambiguous, and often refers to what could rather
+ be referred as quoted graphs, graph literals, IRIs for graphs,
+ knowledge bases, graph stores, etc. The term “Support for Multiple
+ Graphs and Graph Stores” is used as a neutral term in this charter;
+ this term is not and should not be considered as definitive.
+ The Working Group will have to define the right term(s).</blockquote>
+
+ <p>Progress on the design for this feature is tracked under multiple
+ issues:</p>
+
+ <ul>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/5">ISSUE-5: Should we define Graph Literal datatypes?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/14">ISSUE-14: What is a named graph and what should we call it?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/15">ISSUE-15: What is the relationship between the IRI and the triples in a dataset/quad-syntax/etc</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/17">ISSUE-17: How are RDF datasets to be merged?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/22">ISSUE-22: Does multigraph syntax need to support empty graphs?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/28">ISSUE-28: Do we need syntactic nesting of graphs (g-texts) as in N3?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/29">ISSUE-29: Do we support SPARQL's notion of "default graph"?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/30">ISSUE-30: How does SPARQL's notion of RDF dataset relate our notion of multiple graphs?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/32">ISSUE-32: Can we identify both g-boxes and g-snaps?</a></li>
+ <li><a href="http://www.w3.org/2011/rdf-wg/track/issues/33">ISSUE-33: Do we provide a way to refer to sub-graphs and/or individual triples?</a></li>
+ </ul>
+ <p>The design presented here should be considered a straw man proposal at this point. It is based on RDF Datasets as <a href="http://www.w3.org/TR/sparql11-query/#rdfDataset">defined in SPARQL 1.1</a>.</p>
+ </div>
+
+ <p>The RDF data model expresses information as
+ <a title="RDF graph">RDF graphs</a> consisting of
+ <a title="triple">triples</a> with subject, predicate and object.
+ Often, one wants to hold multiple RDF graphs and record information
+ about each graph, allowing an application to work with datasets
+ that involve information from more than one graph.</p>
+
+ <p>An <dfn>RDF Dataset</dfn> is a collection of
+ <a title="RDF graph">RDF graphs</a> and comprises:</p>
+
+ <ul>
+ <li>Exactly one <dfn>default graph</dfn>, being an <a>RDF graph</a>.
+ The default graph does not have a name.</li>
+ <li>Zero or more <dfn title="named graph">named graphs</dfn>.
+ Each named graph is a pair consisting of an <a>IRI</a>
+ (the <dfn>graph name</dfn>), and an <a>RDF graph</a>.
+ Graph names are unique within an RDF dataset.</li>
+ </ul>
+
+</section>
+
+</section>
+
+
+<section id="section-fragID" class="informative">
+ <h2>Fragment Identifiers</h2>
+
+ <p class="issue">This section does not address the case where RDF is
+ embedded in other document formats, such as in RDFa or when an RDF/XML
+ fragment is embedded in SVG. It has been suggested that this may be
+ a general issue for the TAG about the treatment of
+ fragment identifiers when one language is embedded in another. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/issues/37">ISSUE-37</a>.</p>
+
+ <p class="issue">This section treats the RDF/XML media type as
+ canonical for establishing the referent of IRIs that include
+ fragment identifier. Today we have many different media types
+ that can carry RDF graphs, and HTTP content negotiation is more
+ common. Also, the problem addressed in the section
+ (context-dependence of fragment identifiers) has to some extent
+ gone away when RFC 2396 was replaced by RFC 3986. The latter
+ states that the same fragment should be used for the same thing
+ in resources that have multiple representations
+ (Section 3.5 [[URI]]). This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/issues/69">ISSUE-69</a>.</p>
+
+ <p>RDF uses <a title="IRI">IRIs</a>,
+ which may include fragment identifiers, as
+ context free identifiers for resources. RFC 2396 states
+ that the meaning of a fragment
+ identifier depends on the MIME content-type of a document, i.e.
+ is context dependent.</p>
+ <p>These apparently conflicting views are reconciled by
+ considering that an <a>IRI</a> in an RDF graph is treated
+ with respect to the MIME type <code>application/rdf+xml</code>
+ [[RDF-MIME-TYPE]]. Given an IRI that includes a fragment identifier,
+ the fragment identifer identifies the same thing
+ that it does in an <code>application/rdf+xml</code> representation of the
+ resource identified by the IRI excluding the fragment identifier. Thus:</p>
+ <ul>
+ <li>we assume that the IRI excluding fragment
+ identifier identifies a resource, which is presumed to have
+ an RDF representation. So when <code>eg:someurl#frag</code> is used in an RDF
+ document, <code>eg:someurl</code> is taken to
+ designate some RDF document (even when no such document can
+ be retrieved).</li>
+ <li><code>eg:someurl#frag</code> means the thing
+ that is indicated, according to the rules of the
+ <code>application/rdf+xml</code> MIME content-type as
+ a “fragment” or “view” of the RDF document at
+ <code>eg:someurl</code>. If the document does not
+ exist, or cannot be retrieved, or is available only in
+ formats other than <code>application/rdf+xml</code>, then exactly what
+ that view may be is somewhat undetermined, but that does not
+ prevent use of RDF to say things about it.</li>
+ <li>the RDF treatment of a fragment identifier allows it to
+ indicate a thing that is entirely external to the document,
+ or even to the “shared information space” known as the Web.
+ That is, it can be a more general idea, like some particular
+ car or a mythical Unicorn.</li>
+ <li>in this way, an <code>application/rdf+xml</code> document acts as an
+ intermediary between some Web retrievable documents (itself,
+ at least, also any other Web retrievable IRIs that it may
+ use, possibly including schema IRIs and references to other
+ RDF documents), and some set of possibly abstract or non-Web
+ entities that the RDF may describe.</li>
+ </ul>
+ <p>This provides a handling of IRIs and their
+ denotation that is consistent with the RDF model theory and
+ usage, and also with conventional Web behavior. Note that
+ nothing here requires that an RDF application be able to
+ retrieve any representation of resources identified by the IRIs
+ in an RDF graph.</p>
+</section>
+
+
+<section id="section-Acknowledgments" class="informative">
+ <h2>Acknowledgments</h2>
+
+ <p class="issue">This section does not yet list those who made
+ contributions to the RDF 1.1 version, nor does it list the
+ current RDF WG members.</p>
+
+ <p>The RDF 2004 editors acknowledge valuable contributions from
+ Frank Manola, Pat Hayes, Dan Brickley, Jos de Roo,
+ Dave Beckett, Patrick Stickler, Peter F. Patel-Schneider, Jerome Euzenat,
+ Massimo Marchiori, Tim Berners-Lee, Dave Reynolds and Dan Connolly.</p>
+
+ <p>This specification contains a significant contribution from the
+ designers of the RDF typed literal mechanism, Pat
+ Hayes, Sergey Melnik and Patrick Stickler. The document draws upon an earlier
+ RDF Model and Syntax document edited by Ora Lassilla and Ralph Swick,
+ and RDF Schema edited by Dan Brickley and R. V. Guha.</p>
+
+ <p>This specification is a product of extended deliberations by the
+ <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-Acknowledgments">members
+ of the RDFcore Working Group and the RDF and RDF Schema Working Group</a>.</p>
+</section>
+
+
+<section class="appendix informative" id="changes">
+ <h2>Changes from RDF 2004</h2>
+
+ <ul>
+ <li><span class="insert">2011-11-09: Updated the two sections on literals to reflect the </span><a href="http://www.w3.org/2011/rdf-wg/track/issues/71"><span class="insert">ISSUE-71</span></a><span class="insert"> resolution that literals with language tag now have the datatype IRI </span><code><span class="insert">rdf:langString</span></code><span class="insert">. Formally introduced the term “language-tagged string”.</span></li>
+ <li>2011-08-13: Updated Turtle reference to Turtle FPWD</li>
+ <li>2011-07-21: Condensed the 2004 acknowledgements</li>
+ <li>2011-07-21: Updated the two sections on literals to reflect the <a href="http://www.w3.org/2011/rdf-wg/track/issues/12">ISSUE-12</a> resolution that simple literals are no longer part of the abstract syntax. Formally introduced the terms “language-tagged literal”, “simple literal”.</li>
+ <li>2011-07-21: Updated the introduction, and removed many mentions of RDF/XML. Changed the normative reference for the terms in the RDF namespace from the RDF/XML spec to the RDF Schema spec. Removed any mention of the 1999 version of RDF.</li>
+ <li>2011-07-21: Replaced RFC 2279 reference (UTF-8) with RFC 3629</li>
+ <li>2011-07-20: Removed informative sections “Motivations and Goals” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-Overview">RDF 2004 version</a>) and “RDF Expression of Simple Facts” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-SimpleFacts">RDF 2004 version</a>)</li>
+ <li>2011-06-01: Replaced the URI References section with <a href="#section-IRIs">new section on IRIs</a>, and changed “RDF URI Reference” to “IRI” throughout the document.</li>
+ <li>2011-06-01: Changed language tag definition to require well-formedness according to BCP47; added a note that this invalidates some RDF</li>
+ <li>2011-05-25: Added boxes for known WG issues throught the document</li>
+ <li>2011-05-25: Deleted “Structure of this Document” section, it added no value beyond the TOC</li>
+ <li>2011-05-25: Implemented resolution of <a href="http://www.w3.org/2011/rdf-wg/track/issues/40">ISSUE-40: Skolemization advice in the RDF dcocument</a> by adding a section on <a href="#section-skolemization">Replacing Blank Nodes with IRIs</a></li>
+ <li>2011-05-25: rdf:XMLLiteral is disjoint from any datatype not explicitly related to it, per erratum <a href="http://www.w3.org/2001/sw/RDFCore/errata#concept-xmlliteral">[concept-xmlliteral]</a></li>
+ <li>2011-05-25: Added Conformance section with RFC2119 reference</li>
+ <li>2011-05-25: Updated all W3C references to latest editions, and Unicode from v3 to v4</li>
+ <li>2011-05-24: Converted to ReSpec, changed metadata to reflect RDF 1.1</li>
+ </ul>
+</section>
+
+
+<section id="references"></section>
+
+ </body>
+</html>
+
+
--- a/rdf-concepts/index.html Wed Nov 30 07:57:48 2011 -0800
+++ b/rdf-concepts/index.html Wed Nov 30 07:58:22 2011 -0800
@@ -5,6 +5,7 @@
<title>RDF 1.1 Concepts and Abstract Syntax</title>
<style type="text/css">
.figure { font-weight: bold; text-align: center; }
+table.xsd-types td, table.xsd-types th { border: 1px solid #ddd; padding: 0.1em 0.5em; }
</style>
<script src='../ReSpec.js/js/respec.js' class='remove'></script>
<script class='remove'>
@@ -134,7 +135,7 @@
</section>
-<section id="section-Introduction">
+<section id="section-Introduction" class="informative">
<h2>Introduction</h2>
<p class="issue">This document reflects current progress of the RDF Working
@@ -144,308 +145,183 @@
editors expect to work on a number of issues, some of which are
listed in boxes like this throughout the document.</p>
- <p>The Resource Description Framework (RDF) is a framework for
- representing information in the Web.</p>
+ <p>The <em>Resource Description Framework</em> (RDF) is a framework
+ for representing information in the Web.</p>
<p>This document defines an abstract syntax (a data model)
- on which RDF is based,
- and which serves to link concrete syntaxes to its formal
- semantics. It also includes discussion of
- key concepts, datatyping, character normalization
- and handling of IRIs.</p>
-
- <p>Normative documentation of RDF falls into the following
- areas:</p>
+ which serves to link all RDF-based languages and specifications,
+ including:</p>
<ul>
- <li>Serialization syntaxes (Turtle [[TURTLE-TR]], RDFa [[RDFA-PRIMER]], RDF/XML [[RDF-SYNTAX-GRAMMAR]], N-Triples [[N-TRIPLES]]),</li>
-
- <li>the RDF Vocabulary Description Language ([[RDF-SCHEMA]]),</li>
-
- <li>a formal model-theoretic semantics [[!RDF-MT]], and</li>
-
- <li>this document.</li>
- </ul>
-
- <p>The framework is designed so that vocabularies can be layered.
- The terms defined in [[RDF-SCHEMA]] are the first such vocabulary.
- Several other vocabularies for RDF are
- mentioned in the Primer [[RDF-PRIMER]].</p>
-</section>
-
-
-<section id="conformance"></section>
-
+ <li>Serialization syntaxes for storing and exchanging RDF
+ (e.g., <a href="http://www.w3.org/TR/turtle/">Turtle</a> [[TURTLE-TR]]
+ and <a href="http://www.w3.org/TR/REC-rdf-syntax/">RDF/XML</a>
+ [[RDF-SYNTAX-GRAMMAR]]),</li>
-<section id="section-Concepts" class="informative">
- <h2>RDF Concepts</h2>
-
- <p class="issue">This section is quite redundant with later
- normative sections and the RDF Primer. Its removal has been
- proposed. This is
- <a href="http://www.w3.org/2011/rdf-wg/track/issues/68">ISSUE-68</a>.</p>
-
- <p>RDF uses the following key concepts:</p>
+ <li>the <a href="http://www.w3.org/TR/rdf-sparql-query/">SPARQL
+ Query Language</a> [[RDF-SPARQL-QUERY]],</li>
- <ul>
- <li>Graph data model</li>
-
- <li>IRI-based vocabulary</li>
+ <li>the <a href="http://www.w3.org/TR/rdf-schema/">RDF Vocabulary
+ Description Language</a> [[RDF-SCHEMA]],</li>
- <li>Datatypes</li>
-
- <li>Literals</li>
-
- <li>Entailment</li>
+ <li>a <a href="http://www.w3.org/TR/rdf-mt/">formal
+ model-theoretic semantics for RDF</a> [[RDF-MT]].</li>
</ul>
-<section id="section-data-model">
- <h3>Graph Data Model</h3>
+<section id="data-model">
+ <h3>Graph-based Data Model</h3>
- <p>The underlying structure of any expression in RDF is a
- collection of triples, each consisting of a subject, a
- predicate and an object. A set of such triples is called an RDF
- graph (defined more formally in
-<a href="#section-Graph-syntax">section 6</a>). This can be
- illustrated by a node and directed-arc diagram, in which each
- triple is represented as a node-arc-node link (hence the term
- “graph”).</p>
+ <p>The core structure of the abstract syntax is a collection of
+ <a title="RDF triple">triples</a>, each consisting of a <a>subject</a>,
+ a <a>predicate</a> and an <a>object</a>. A set of such triples is called
+ an <a>RDF graph</a>. This can be illustrated by a node and
+ directed-arc diagram, in which each triple is represented as a
+ node-arc-node link; hence the term “graph”.</p>
<div class="figure">
<img src="Graph-ex.gif" alt="image of the RDF triple comprising (subject, predicate, object)" />
</div>
- <p>Each triple represents a statement of a relationship between
- the things denoted by the nodes that it links. Each triple has
- three parts:</p>
- <ol>
- <li>a <a>subject</a>,</li>
- <li>an <a>object</a>, and</li>
- <li>a <a>predicate</a> (also called a
- <a>property</a>) that denotes a
- relationship.</li>
- </ol>
- <p>The direction of the arc is significant: it always points
- toward the object.</p>
- <p>The <a title="node">nodes</a> of an RDF graph
- are its subjects and objects.</p>
- <p>The assertion of an RDF triple says that some relationship,
- indicated by the predicate, holds between the things denoted by
- subject and object of the triple. The assertion of an RDF graph
- amounts to asserting all the triples in it, so the meaning of
- an RDF graph is the conjunction (logical AND) of the statements
- corresponding to all the triples it contains. A formal account
- of the meaning of RDF graphs is given in [[!RDF-MT]].</p>
-</section>
-
-
-<section id="section-IRI-Vocabulary">
- <h3>IRI-based Vocabulary and Node Identification</h3>
-
- <p>A <a>node</a> may be an <a>IRI</a>, a <a>literal</a>,
- or <a title="blank node">blank</a> (having no separate form of identification).
- Properties are <a title="IRI">IRIs</a>.</p>
- <p>An <a>IRI</a> or <a>literal</a> used as a node identifies what
- that node represents. An IRI used as a predicate
- identifies a relationship between the things represented by the nodes it connects. A
- predicate IRI may also be a node in the graph.</p>
- <p>A <a>blank node</a> is a node that is
- not an IRI or a literal. In the RDF abstract syntax, a
- blank node is just a unique node that can be used in one or
- more RDF statements.</p>
- <p>A convention used by some linear representations of an RDF
- graph to allow several statements to use the same
- blank node is to use a <dfn>blank node
- identifier</dfn>, which is a local identifier that can be
- distinguished from all IRIs and literals. When graphs are
- merged, their blank nodes must be kept distinct if meaning is
- to be preserved; this may call for re-allocation of blank node
- identifiers. Note that such blank node identifiers are not part
- of the RDF abstract syntax, and the representation of triples
- containing blank nodes is entirely dependent on the particular
- concrete syntax used.</p>
+ <p>There may be three kinds of <a title="node">nodes</a> in an
+ <a>RDF graph</a>: <a title="IRI">IRIs</a>, <a title="literal">literals</a>,
+ and <a title="blank node">blank nodes</a>.</p>
</section>
-<section id="section-Datatypes-intro">
- <h3>Datatypes</h3>
-
- <p>Datatypes are used by RDF in the representation of values such
- as integers, floating point numbers and dates.</p>
-
- <p>
-A datatype consists of a lexical space, a value space and a lexical-to-value
-mapping, see <a href="#section-Datatypes">section 5</a>.
-</p>
-
- <p>For example, the lexical-to-value mapping for the XML Schema datatype
- <var>xsd:boolean</var>, where each member of the value space
- (represented here as 'T' and 'F') has two lexical representations,
- is as follows:</p>
-
- <table border="1" cellpadding="5" summary=
- "A table detailing the xsd:boolean datatype.">
- <tr>
- <th align="left">Value Space</th>
-
- <td>{T, F}</td>
- </tr>
-
- <tr>
- <th align="left">Lexical Space</th>
+<section id="resources-and-statements">
+ <h3>Resources and Statements</h3>
- <td>{"0", "1", "true", "false"}</td>
- </tr>
-
- <tr>
- <th align="left">Lexical-to-Value Mapping</th>
-
- <td>{<"true", T>, <"1", T>, <"0", F>,
- <"false", F>}</td>
- </tr>
- </table>
+ <p>Any <a>IRI</a> and <a>literal</a> <dfn title="denote">denotes</dfn>
+ some thing in the universe of discourse. These things are called
+ <dfn title="resource">resources</dfn>. Anything can be a resource,
+ including physical things, documents, and abstract concepts.
+ The resource denoted by an IRI is called its <a>referent</a>, and the
+ resource denoted by a literal is called its
+ <a title="literal value">value</a>. Literals have
+ <a title="datatype">datatypes</a> that define the range of possible
+ values, such as strings, numbers, and dates. A special kind of literals,
+ <a>language-tagged strings</a>, denote plain-text strings in a
+ natural language.</p>
- <p>RDF predefines just one datatype <code><a>rdf:XMLLiteral</a></code>, used for
- embedding XML in RDF (see <a href="#section-XMLLiteral">section
- 5.1</a>).</p>
+ <p>The assertion of an <a>RDF triple</a> says that <em>some relationship,
+ indicated by the <a>predicate</a>, holds between the
+ <a title="resource">resources</a> <a title="denote">denoted</a> by
+ the <a>subject</a> and <a>object</a></em>. This statement corresponding
+ to an RDF triple is known as an <dfn>RDF statement</dfn>.
+ The predicate itself is an <a>IRI</a> and denotes a binary relation,
+ also known as a <dfn>property</dfn>. (Relations that involve more than
+ two entities can only be
+ <a href="http://www.w3.org/TR/swbp-n-aryRelations/">indirectly
+ expressed in RDF</a> [[SWBP-N-ARYRELATIONS]].)</p>
- <p>There is no built-in concept of numbers or dates or other common
- values. Rather, RDF defers to datatypes that are defined
- separately, and identified with <a title="IRI">IRIs</a>.
- The predefined XML Schema
- datatypes [[!XMLSCHEMA-2]] are expected
- to be widely used for this purpose.</p>
+ <p>The assertion of an <a>RDF graph</a> amounts to asserting all the
+ triples in it, so the meaning of an RDF graph is the conjunction
+ (logical AND) of the <a title="RDF statement">statements</a>
+ corresponding to all the triples it contains.</p>
-
- <p>RDF provides no mechanism for defining new datatypes. XML Schema
- Datatypes [[!XMLSCHEMA-2]] provides an
- extensibility framework suitable for defining new datatypes for use
- in RDF.</p>
+ <p><a title="RDF statement">Statements</a> involving
+ <a title="blank node">blank nodes</a> say that something with the given
+ relationships exists, without explicitly naming it.</p>
</section>
-<section id="section-Literals">
- <h3>Literals</h3>
+<section id="referents">
+ <h3>The Referent of an IRI</h3>
- <p><a title="literal">Literals</a> are used to identify values such as numbers and dates
- by means of a lexical representation. Anything represented by a
- literal could also be represented by an <a>IRI</a>, but it is often more
- convenient or intuitive to use literals.</p>
-
- <p>A literal may be the object of an RDF statement, but not the
- subject or the predicate.</p>
-
- <p>Literals may be <cite>typed</cite> or <cite>language-tagged</cite>:</p>
+ <p>The <a>resource</a> <a title="denote">denoted</a> by an <a>IRI</a>
+ is also called its <dfn>referent</dfn>.
+ What exactly is denoted by any given IRI is not defined by this
+ specification. The question is treated in other documents like
+ <em><a href="http://www.w3.org/TR/webarch/">Architecture of the
+ World Wide Web, Volume One</a></em> [[WEBARCH]] and
+ <em><a href="http://www.w3.org/TR/cooluris/">Cool URIs for the
+ Semantic Web</a></em> [[COOLURIS]].
+ A very brief, informal and partial account follows:</p>
<ul>
- <li>A <a>typed literal</a> is a string combined with a
- <a>datatype IRI</a>. It denotes the
- member of the identified datatype's value space obtained by
- applying the lexical-to-value mapping to the literal string.</li>
+ <li>By social convention, the
+ <a href="http://www.w3.org/TR/webarch/#uri-ownership">IRI owner</a>
+ [[WEBARCH]] gets to say what an <a>IRI</a> <a title="denote">denotes</a>.
+ They do this when “<dfn>minting</dfn>” a new IRI.</li>
- <li>A <a>language-tagged literal</a> is a string combined
- with a language tag. This may be used for
- plain text in a natural language. Language-tagged literals
- are self-denoting.</li>
+ <li>The IRI owner can establish the intended <a>referent</a>
+ by means of a specification or other document that explains
+ what is denoted. For example, [[RDF-SCHEMA]] specifies the referents
+ of various IRIs that start with
+ <code>http://www.w3.org/2000/01/rdf-schema#</code>.</li>
+
+ <li>A good way of communicating the intended referent to the world
+ is to set up the IRI so that it resolves to such a document.</li>
+
+ <li>Such a document can, in fact, be an <a>RDF document</a>
+ that describes the denoted resource by means of
+ <a title="RDF statement">RDF statements</a>.</li>
</ul>
- <p>Continuing the example from <a href="#section-Datatypes-intro">section
- 3.3</a>, the typed literals that can be defined using the XML
- Schema datatype <var>xsd:boolean</var> are:</p>
-
- <table border="1" cellpadding="5" summary=
- "This table lists the literals of type xsd:boolean.">
- <tr>
- <th>Typed Literal</th>
-
- <th>Lexical-to-Value Mapping</th>
-
- <th>Value</th>
- </tr>
-
- <tr>
- <td align="center"><xsd:boolean, "true"></td>
-
- <td align="center"><"true", T></td>
-
- <td align="center">T</td>
- </tr>
-
- <tr>
- <td align="center"><xsd:boolean, "1"></td>
-
- <td align="center"><"1", T></td>
-
- <td align="center">T</td>
- </tr>
-
- <tr>
- <td align="center"><xsd:boolean, "false"></td>
+ <p>An <dfn>RDF vocabulary</dfn> is a collection of <a title="IRI">IRIs</a>
+ with clearly established <a title="referent">referents</a>
+ intended for use in <a title="RDF graph">RDF graphs</a>. For example,
+ the IRIs documented in [[RDF-SCHEMA]] are the RDF Schema vocabulary.
+ RDF Schema can itself be used to define and document additional
+ RDF vocabularies. Some such vocabularies are mentioned in the
+ Primer [[RDF-PRIMER]].</p>
+</section>
- <td align="center"><"false", F></td>
-
- <td align="center">F</td>
- </tr>
-
- <tr>
- <td align="center"><xsd:boolean, "0"></td>
-
- <td align="center"><"0", F></td>
-
- <td align="center">F</td>
- </tr>
- </table>
- <p>For text that may contain
- markup, use typed literals
-with type <a href="#section-XMLLiteral">rdf:XMLLiteral</a>.
-If language annotation is required,
-it must be explicitly included as markup, usually by means of an
-<code>xml:lang</code> attribute.
-XHTML [[XHTML10]] may be included within RDF
-in this way. Sometimes, in this latter case,
- an additional <code>span</code> or <code>div</code>
- element is needed to carry an
-<code>xml:lang</code> or <code>lang</code> attribute.
- </p>
+<section id="entailment">
+ <h3>Formal Meaning and Entailment</h3>
-<p class="issue">Update the XHTML 1.0 reference to something more recent?</p>
+ <p>The idea of meaning in RDF is underpinned by the formal concept
+ of <dfn>entailment</dfn>. In brief, an <a>RDF graph</a> <em>A</em>
+ is said to <em>entail</em> another RDF graph <em>B</em> if every
+ possible arrangement of things in the world that makes <em>A</em> true
+ also makes <em>B</em> true. On this basis, if the truth of <em>A</em>
+ is presumed or demonstrated then the truth of <em>B</em> can be inferred.
+ An account of meaning and entailment in RDF, using the formalism of
+ model theory, is given in [[RDF-MT]].</p>
+</section>
-<p>
-The string in both plain and typed literals is recommended to
-be in Unicode Normal Form C [[!NFC]]. This is motivated
-by [[CHARMOD]] particularly
-<a href="http://www.w3.org/TR/2003/WD-charmod-20030822/#sec-Normalization">section 4
-Early Uniform Normalization</a>.
-</p>
+
+<section id="managing-graphs">
+ <h3>Merging and Managing RDF Graphs</h3>
+
+ <p class="issue">This section should explain terminology around working
+ with multiple graphs, and explain the fact that graphs merge easily.
+ This will be added once the Working Group has finalised a design.</p>
+
+ <p>An <dfn>RDF document</dfn> is a document that encodes an
+ <a>RDF graph</a> in a <dfn>concrete RDF syntax</dfn>, such as
+ Turtle [[TURTLE-TR]], RDFa [[RDFA-PRIMER]], RDF/XML [[RDF-SYNTAX-GRAMMAR]],
+ or N-Triples [[N-TRIPLES]].</p>
+</section>
+
</section>
-<section id="section-Entailment">
- <h3>Entailment</h3>
-
- <p>The ideas on meaning and inference in RDF are underpinned by the
- formal concept of <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#entail">
-<cite>entailment</cite></a>, as
- discussed in the RDF
- semantics document [[!RDF-MT]].
-In brief, an RDF expression A is said to
-<dfn title="entailment">entail</dfn> another RDF expression B
-if every possible
-arrangement of things in the world that makes A true also makes B
-true. On this basis, if the truth of A is presumed or demonstrated
-then the truth of B can be inferred .
-</p>
-</section>
-
+<section id="conformance">
+ Implementations are free to represent <a title="RDF graph">RDF graphs</a> in
+ any other equivalent form. As an example: in an RDF graph,
+ literals with datatype <tt><a>rdf:XMLLiteral</a></tt> can be represented
+ in a non-canonical
+ format, and canonicalization performed during the comparison between two
+ such literals. In this example the comparisons may be
+ being performed either between syntactic structures or
+ between their denotations in the domain of discourse.
+ Implementations that do not require any such comparisons can
+ hence be optimized.</p>
</section>
<section id="section-URIspaces">
<h2>RDF Vocabulary IRI and Namespace</h2>
+ <p class="issue">This section should be removed from
+ <em>RDF Concepts</em> and folded into [[RDF-SCHEMA]] which
+ actually defines the terms in question. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/actions/121">ACTION-121</a>.</p>
+
<p>RDF uses <a title="IRI">IRIs</a> to identify resources
and properties. Certain
IRIs with the following leading substring are defined by the
@@ -470,216 +346,38 @@
</section>
-<section id="section-Datatypes">
- <h2>Datatypes</h2>
-
- <p class="issue">This section perhaps should discuss
- <a href="http://www.w3.org/TR/rdf-mt/#dtype_interp">the XSD datatype map</a>
- and <code><a href="http://www.w3.org/TR/rdf-plain-literal/">rdf:PlainLiteral</a></code>.
- This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/70">ISSUE-70</a>.</p>
-
-<p>
-The datatype abstraction used in RDF is compatible with
-the abstraction used in
-XML Schema Part 2:
- Datatypes [[!XMLSCHEMA-2]].</p>
-<p>
-A datatype consists of a lexical space, a value space and a lexical-to-value
-mapping.
-</p>
-<p>The <dfn>lexical space</dfn> of a datatype is a set of Unicode [[!UNICODE]] strings.</p>
-<p>
-The <dfn>lexical-to-value mapping</dfn> of a datatype is a set of pairs whose
-first element belongs to
-the <a>lexical space</a> of the datatype,
-and the second element belongs to the
- <dfn>value space</dfn> of the datatype:
-</p>
-<ul>
-<li>
-Each member of the lexical space is paired with (maps to) exactly one member
-of the value space.
-</li>
-<li>
-Each member of the value space may be paired with any number (including
-zero) of members of the lexical space (lexical representations for that
-value).
-</li>
-</ul>
-<p>
-A datatype is identified by one or more IRIs.
-</p>
-<p>
-RDF may be used with any datatype definition that conforms to this
-abstraction, even if not defined in terms of XML Schema.
-</p>
- <p>Certain XML Schema built-in datatypes are not suitable for use
- within RDF. For example, the
-<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#QName">QName</a>
-datatype requires a namespace declaration to be in scope during
- the mapping, and is not recommended for use in RDF.
- [[!RDF-MT]] contains a
-<a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#dtype_interp">more detailed discussion</a>
- of specific XML Schema built-in datatypes. </p>
-
-<div class="note">
-<p>When the datatype is defined using XML Schema:
-</p>
-<ul>
-<li>
-All values correspond to some lexical form, either using
-the lexical-to-value mapping of the datatype or if it is a union
-datatype with a lexical mapping associated with one of the member
-datatypes.
-</li>
-<li>
-XML Schema facets remain part of the datatype and are used by the XML
-Schema mechanisms that control the lexical space and the value space;
-however, RDF does not define a standard mechanism to access these facets.</li>
-
-<li>In [[XMLSCHEMA-1]],
-<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#section-White-Space-Normalization-during-Validation">
-white space normalization</a> occurs
-during
-<a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/#key-vn">validation</a>
-according to the value of the
-<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#rf-whiteSpace">whiteSpace
-facet</a>. The lexical-to-value mapping used in RDF datatyping
-occurs after this, so that the whiteSpace facet has no
-effect in RDF datatyping.
-</li>
-</ul>
-
-</div>
-
-
-<section id="section-XMLLiteral">
- <h3>XML Content within an RDF Graph</h3>
-
- <p class="issue">The canonicalization rules required for XML literals
- are quite complicated. Increasingly, RDF is produced and consumed in
- environments where no XML parser and canonicalization engine is
- available. A possible change to relax the requirements for the
- lexical space, while retaining the value space, is under discussion.
- This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/13">ISSUE-13</a>.</p>
-
- <p>RDF provides for XML content as a possible literal value.
- Such content is indicated in an RDF graph using a typed literal
- whose datatype is a special built-in datatype
- <dfn>rdf:XMLLiteral</dfn>,
- defined as follows.</p>
+<section id="section-rdf-graph">
+ <h2>RDF Graphs</h2>
-
- <dl>
- <dt><a name="XMLLiteral-uri" id="XMLLiteral-uri">An IRI for
-identifying this datatype</a></dt>
-
- <dd>is
- <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>.</dd>
-
-
-
-
- <dt><a name="XMLLiteral-lexical-space" id="XMLLiteral-lexical-space">The lexical space</a></dt>
-
-<dd>is the set of all
-strings:
-<ul>
-<li>which are well-balanced, self-contained
-<a href="http://www.w3.org/TR/2000/REC-xml-20001006#NT-content">
-XML content</a>
-[[!XML10]];
-</li>
-<li>for which encoding as UTF-8
-[[!UTF-8]] yields
-<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-exclusive-canonical-XML">
-exclusive
-Canonical XML </a> (with comments, with empty
-<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-InclusiveNamespaces-PrefixList">
-InclusiveNamespaces PrefixList
-</a>) [[!XML-EXC-C14N]];
-</li>
-<li>for which embedding between an arbitrary XML start tag and an end tag
-yields a document conforming to <a href=
- "http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
- Namespaces</a> [[!XML-NAMES]]</li>
-</ul>
-</dd>
-
-
- <dt><a name="XMLLiteral-value-space" id="XMLLiteral-value-space">The value space</a></dt>
-
- <dd>is a set of entities, called XML values, which is:
-<ul>
-<li>disjoint from the lexical space;</li>
-<li>disjoint from the value space of any other datatype that is not explicitly defined as a sub- or supertype of this datatype;</li>
-<li>disjoint from the set of Unicode character strings [[!UNICODE]];</li>
-<li>and in 1:1 correspondence with the lexical space.</li>
-</ul>
-</dd>
-
- <dt><a name="XMLLiteral-mapping" id="XMLLiteral-mapping">The lexical-to-value mapping</a></dt>
+ <p>An <dfn>RDF graph</dfn> is a set of
+ <a title="RDF triple">RDF triples</a>.</p>
- <dd>
-is a one-one mapping from the lexical space onto the value space,
- i.e. it is both injective and surjective.
-</dd>
-
-
-
- </dl>
-
- <p class="note">Not all values of this datatype are compliant
- with XML 1.1 [[XML11]]. If compliance
- with XML 1.1 is desired, then only those values that are
-<a href="http://www.w3.org/TR/2002/CR-xml11-20021015/#sec2.13">fully
- normalized</a> according to XML 1.1 should be used.</p>
-
- <p class="note">XML values can be thought of as the
-[[XML-INFOSET]] or the [[XPATH]]
-nodeset corresponding to the lexical form, with an appropriate equality
-function.</p>
-
- <p class="note">RDF applications may use additional equivalence relations, such as
-that which relates an
-<a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#string"><code>xsd:string</code></a>
-
-with an <code>rdf:XMLLiteral</code> corresponding to
-a single text node of the same string.</p>
+ <p><a name="section-graph-equality"></a><dfn>Graph equivalence</dfn>:
+ Two <a title="RDF graph">RDF graphs</a>
+ <var>G</var> and <var>G'</var> are equivalent if there
+ is a bijection <var>M</var> between the sets of nodes of the two graphs,
+ such that:</p>
-</section>
-
-</section>
-
-
-<section id="section-Graph-syntax">
- <h2>Abstract Syntax</h2>
-
- <p>This section defines the RDF abstract syntax. The RDF abstract
- syntax is a set of triples, called the RDF graph.</p>
+ <ol>
+ <li><var>M</var> maps blank nodes to blank nodes.</li>
+ <li><var>M(lit)=lit</var> for all <a title="literal">RDF literals</a> <var>lit</var> which
+ are nodes of <var>G</var>.</li>
- <p>This section also defines equivalence between RDF graphs. A
- definition of equivalence is needed to support the RDF Test Cases
- [[RDF-TESTCASES]] specification.</p>
+ <li><var>M(uri)=uri</var> for all <a title="IRI">IRIs</a> <var>uri</var>
+ which are nodes of <var>G</var>.</li>
-<p class="note">This <em>abstract</em> syntax is the
-syntax over which the formal semantics are defined.
-Implementations are free to represent RDF graphs in
-any other equivalent form. As an example:
-in an RDF graph,
-literals with datatype <tt>rdf:XMLLiteral</tt> can be represented
-in a non-canonical
-format, and canonicalization performed during the comparison between two
-such literals. In this example the comparisons may be
-being performed either between syntactic structures or
-between their denotations in the domain of discourse.
-Implementations that do not require any such comparisons can
-hence be optimized.
-</p>
+ <li>The triple <var>( s, p, o )</var> is in <var>G</var> if and
+ only if the triple <var>( M(s), p, M(o) )</var> is in
+ <var>G'</var></li>
+ </ol>
+ <p>With this definition, <var>M</var> shows how each blank node
+ in <var>G</var> can be replaced with
+ a new blank node to give <var>G'</var>. A definition of graph equivalence
+ is needed to support the RDF Test Cases [[RDF-TESTCASES]] specification.</p>
<section id="section-triples">
- <h3>RDF Triples</h3>
+ <h3>Triples</h3>
<p>An <dfn>RDF triple</dfn> contains three components:</p>
@@ -698,47 +396,16 @@
<p>The predicate is also known as the <dfn>property</dfn> of the triple.</p>
+ <p>The set of <dfn title="node">nodes</dfn> of an <a>RDF graph</a>
+ is the set of subjects and objects of triples in the graph.
+ Predicate IRIs MAY also appear as nodes in the graph.</p>
+
<p><a title="IRI">IRIs</a>, <a title="blank node">blank nodes</a> and
<a title="literal">literals</a> are collectively known as
<dfn title="RDF term">RDF terms</dfn>.</p>
</section>
-<section id="section-rdf-graph">
- <h3>RDF Graph</h3>
-
- <p>An <dfn>RDF graph</dfn> is a set of RDF triples.</p>
-
- <p>The set of <dfn title="node">nodes</dfn> of an RDF graph is the set of subjects and objects of
- triples in the graph.</p>
-</section>
-
-
-<section id="section-graph-equality">
- <h3>Graph Equivalence</h3>
-
- <p>Two <a title="RDF graph">RDF graphs</a> <var>G</var> and <var>G'</var> are equivalent if there
- is a bijection <var>M</var> between the sets of nodes of the two graphs,
- such that:</p>
-
- <ol>
- <li><var>M</var> maps blank nodes to blank nodes.</li>
- <li><var>M(lit)=lit</var> for all <a title="literal">RDF literals</a> <var>lit</var> which
- are nodes of <var>G</var>.</li>
-
- <li><var>M(uri)=uri</var> for all <a title="IRI">IRIs</a> <var>uri</var>
- which are nodes of <var>G</var>.</li>
-
- <li>The triple <var>( s, p, o )</var> is in <var>G</var> if and
- only if the triple <var>( M(s), p, M(o) )</var> is in
- <var>G'</var></li>
- </ol>
- <p>With this definition, <var>M</var> shows how each blank node
- in <var>G</var> can be replaced with
- a new blank node to give <var>G'</var>.</p>
-</section>
-
-
<section id="section-IRIs">
<h3>IRIs</h3>
@@ -752,7 +419,8 @@
<p>IRIs in the RDF abstract syntax MUST be absolute, and MAY
contain a fragment identifier.</p>
- <p>Two IRIs are equal if and only if they are equivalent
+ <p><dfn>IRI equality</dfn>:
+ Two IRIs are equal if and only if they are equivalent
under Simple String Comparison according to
<a href="http://tools.ietf.org/html/rfc3987#section-5.1">section 5.1</a>
of [[!IRI]]. Further normalization MUST NOT be performed when
@@ -815,46 +483,54 @@
<section id="section-Graph-Literal">
- <h3>RDF Literals</h3>
-
- <p class="issue">This section is a major departure from RDF 2004
- as <a title="simple literal">simple literals</a> are now treated
- as syntactic sugar for <code>xsd:string</code>
- <a title="typed literal">typed literals</a>. Further changes
- to RDF's literal design are under consideration:
- <a title="language-tagged literal">Language-tagged literals</a>
- may receive a datatype, and
- <a href="http://www.w3.org/TR/rdf-plain-literal/"><code>rdf:PlainLiteral</code>s</a> [[RDF-PLAINLITERAL]]
- may be folded into the design somehow. This is
- <a href="http://www.w3.org/2011/rdf-wg/track/issues/71">ISSUE-71</a>.</p>
+ <h2>Literals</h2>
- <p>A <dfn>literal</dfn> in an <a>RDF graph</a> is either a
- <a>typed literal</a> or a <a>language-tagged literal</a>.</p>
-
- <p>All literals have a <dfn>lexical form</dfn> being a Unicode
- [[!UNICODE]] string, which SHOULD be in Normal Form C [[!NFC]].</p>
+ <p>Literals are used to denote values such as strings, numbers and dates
+ by means of a lexical representation.</p>
- <p><dfn title="language-tagged literal">Language-tagged literals</dfn> have
- a <a>lexical form</a> and a non-empty <dfn>language tag</dfn> as
- defined by [[!BCP47]]. The language tag MUST be well-formed according to
+ <p>A <dfn>literal</dfn> in an <a>RDF graph</a> consists of:</p>
+
+ <ul>
+ <li>a <dfn>lexical form</dfn> being a Unicode [[!UNICODE]] string,
+ which should be in Normal Form C [[!NFC]],</li>
+ <li>a <dfn>datatype IRI</dfn> being an <a>IRI</a> that establishes
+ the <a>literal value</a>.</li>
+ </ul>
+
+ <p>A <dfn>language-tagged string</dfn> is any <a>literal</a>
+ whose <a>datatype IRI</a> is equal to
+ <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#langString</code>.
+ In addition to <a>lexical form</a> and datatype IRI,
+ a language-tagged string also has:</p>
+
+ <ul>
+ <li>a non-empty <dfn>language tag</dfn> as defined by [[!BCP47]].
+ The language tag MUST be well-formed according to
<a href="http://tools.ietf.org/html/bcp47#section-2.2.9">section 2.2.9</a>
- of [[!BCP47]], and MUST be normalized to lowercase.</p>
+ of [[!BCP47]], and MUST be normalized to lowercase.</li>
+ </ul>
- <p><dfn title="typed literal">Typed literals</dfn> have a <a>lexical form</a>
- and a <dfn>datatype IRI</dfn> being an <a>IRI</a>.</p>
-
<p>Concrete syntaxes MAY support <dfn title="simple literal">simple
literals</dfn>, consisting of only a <a>lexical form</a>
- without any language tag or datatype IRI. Simple literals only
+ without any datatype IRI or language tag. Simple literals only
exist in concrete syntaxes, and are treated as
syntactic sugar for abstract syntax
- <a title="plain literal">typed literals</a> with the datatype IRI
- <code>http://www.w3.org/2001/XMLSchema#string</code>.
- Simple literals and <a>language-tagged literals</a> are
- collectively known as <dfn title="plain literal">plain literals</dfn>.</p>
+ <a title="literal">literals</a> with the <a>datatype IRI</a>
+ <code>http://www.w3.org/2001/XMLSchema#string</code>.</p>
- <p class="note">Earlier versions of RDF allowed
- <a title="simple literal">simple literals</a> in the abstract syntax.</p>
+ <p><dfn>Literal equality</dfn>:
+ Two literals are equal if and only if the two
+ <a title="lexical form">lexical forms</a>, the two
+ <a title="datatype IRI">datatype IRIs</a>, and the two
+ <a title="language tag">language tags</a> (if any)
+ compare equal, character by character.</p>
+
+ <p class="note">In earlier versions of RDF, literals with a
+ <a>language tag</a> did not have a <a>datatype IRI</a>, and
+ <a title="simple literal">simple literals</a> could appear
+ directly in the abstract syntax. Simple literals and literals with a
+ language tag were collectively known as
+ <dfn title="plain literal">plain literals</dfn>.</p>
<p class="note">Literals in which the lexical form begins with a
composing character (as defined by [[CHARMOD]]) are allowed however they may cause
@@ -865,6 +541,13 @@
but were not well-formed according to [[!BCP47]]. Such
language tags do not conform to RDF 1.1.</p>
+ <p class="note">The <code>xsd:string</code> datatype does not
+ permit the <code>#x0</code> character, and implementations may not permit
+ control codes in the <code>#x1-#x1F</code> range. Earlier versions of
+ RDF allowed these characters in
+ <a title="simple literal">simple literals</a>, although they
+ could never be serialized in a W3C-recommended concrete syntax.</p>
+
<p class="note">When using the language tag, care must be
taken not to confuse language with locale. The language
tag relates only to human language text. Presentational
@@ -879,104 +562,40 @@
of comparing two language tags should not be sensitive to the case of
the original input.</p>
-
-<section id="section-Literal-Equality">
- <h4>Literal Equality</h4>
-
- <p>Two literals are equal if and only if all of the following
- hold:</p>
-
- <ul>
- <li>The strings of the two lexical forms compare equal, character
- by character.</li>
-
- <li>Either both or neither have language tags.</li>
-
- <li>The language tags, if any, compare
- equal.</li>
-
- <li>Either both or neither have datatype IRIs.</li>
-
- <li>The two datatype IRIs, if any, compare equal, character by
- character.</li>
- </ul>
-
- <p class="note">RDF Literals are distinct and distinguishable
- from <a title="IRI">IRIs</a>; e.g. <code>http://example.org/</code> as an RDF
- Literal (untyped, without a language tag) is not equal to
- <code>http://example.org/</code> as an IRI.</p>
-</section>
-
-
-<section id="section-Literal-Value">
- <h4>The Value Corresponding to a Typed Literal</h4>
+ <p class="note">RDF Literals are distinct and distinguishable
+ from <a title="IRI">IRIs</a>; e.g. <code>http://example.org/</code>
+ as a string <a>literal</a> is not equal to <code>http://example.org/</code>
+ as an IRI.</p>
- <p>The datatype IRI refers to a <a href=
- "#section-Datatypes">datatype</a>. For XML Schema <a href=
- "http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#built-in-datatypes">
- built-in</a> datatypes, IRIs such as
- <code>http://www.w3.org/2001/XMLSchema#int</code> are used. The IRI
- of the datatype <a href="#section-XMLLiteral"><tt>rdf:XMLLiteral</tt></a> may be used.
- There may be other, implementation dependent, mechanisms by which
- IRIs refer to datatypes.</p>
-
- <p>The <em>value</em> associated with a typed literal is found by
- applying the lexical-to-value mapping associated with the datatype IRI to
- the lexical form.
- </p>
-
- <p>
- If the lexical form is not in
- the lexical space of the datatype associated with the datatype IRI,
-then no literal value can be associated with the typed literal.
-Such a case, while in error, is not <em>syntactically</em> ill-formed.</p>
-<!--
- <p>A typed literal for which the datatype does not map the lexical
- form to a value is not syntactically ill-formed.</p>
--->
-
-
- <p class="note">
-In application contexts, comparing the values of typed literals (see
-<a href="#section-Literal-Value">
-section
-6.5.2</a>)
-is usually more helpful than comparing their syntactic forms (see
-<a href="#section-Literal-Equality">
-section
-6.5.1</a>).
-Similarly, for comparing RDF Graphs,
-semantic notions of entailment (see
-[[!RDF-MT]]) are usually
-more helpful than syntactic equality (see
-<a href="#section-graph-equality">
-section
-6.3</a>).</p>
-
-</section>
</section>
<section id="section-blank-nodes">
- <h3>Blank Nodes</h3>
+ <h2>Blank Nodes</h2>
-<p>
-The <dfn title="blank node">blank nodes</dfn> in an RDF graph
-are drawn from an infinite set.
-This set of blank nodes, the set of all <a title="IRI">IRIs</a>
-and the set of all <a title="literal">literals</a> are pairwise disjoint.
-</p>
-<p>
-Otherwise, this set of blank nodes is arbitrary.
-</p>
-<p>RDF makes no reference to any internal structure of blank nodes.
-Given two blank nodes, it is
-possible to determine whether or not they are the same.</p>
+ <p>The <dfn title="blank node">blank nodes</dfn> in an RDF graph
+ are drawn from an infinite set. This set is disjoint from the set
+ of all <a title="IRI">IRIs</a> and the set of all
+ <a title="literal">literals</a>.
+ Otherwise, this set of blank nodes is arbitrary.</p>
+
+ <p>RDF makes no reference to any internal structure of blank nodes.
+ Given two blank nodes, it is
+ possible to determine whether or not they are the same.</p>
+
+ <p class="note">Some concrete syntaxes for RDF use
+ <dfn title="blank node identifier">blank node identifiers</dfn>
+ to allow several statements to use the same
+ blank node. A blank node identifier is a local identifier that can be
+ distinguished from IRIs and literals. Such blank node identifiers are
+ <em>not</em> part of the RDF abstract syntax, but are entirely
+ dependent on the particular concrete syntax used.</p>
+</section>
<section id="section-skolemization">
- <h4>Replacing Blank Nodes with IRIs</h4>
+ <h3>Replacing Blank Nodes with IRIs</h3>
<p>Blank nodes do not have identifiers in the RDF abstract syntax. The
<a title="blank node identifier">blank node identifiers</a> introduced
@@ -1007,7 +626,8 @@
<pre>http://example.com/.well-known/genid/d26a2d0e98334696f4ad70a677abc1f6</pre>
<p class="issue">IETF registration of the <code>genid</code> name is
- currently in progress.</p>
+ currently in progress. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/actions/82">ACTION-82</a>.</p>
<p class="note">RFC 5785 [[WELL-KNOWN]] only specifies well-known URIs,
not IRIs. For the purpose of this document, a well-known IRI is any
@@ -1017,9 +637,415 @@
</section>
+<section id="section-Datatypes">
+ <h2>Datatypes</h2>
+
+ <p>Datatypes are used with RDF <a title="literal">literals</a>
+ to represent values such as string, numbers and dates.
+ The datatype abstraction used in RDF is compatible with XML Schema
+ [[!XMLSCHEMA11-2]]. Any datatype definition that conforms
+ to this abstraction MAY be used in RDF, even if not defined
+ in terms of XML Schema. RDF re-uses the XML Schema built-in datatypes,
+ and provides one additional built-in datatype,
+ <code><a>rdf:XMLLiteral</a></code>.</p>
+
+ <p>A <dfn>datatype</dfn> consists of a <a>lexical space</a>,
+ a <a>value space</a> and a <a>lexical-to-value mapping</a>, and
+ is denoted by one or more <a title="IRI">IRIs</a>.</p>
+
+<p>The <dfn>lexical space</dfn> of a datatype is a set of Unicode [[!UNICODE]] strings.</p>
+<p>
+The <dfn>lexical-to-value mapping</dfn> of a datatype is a set of pairs whose
+first element belongs to
+the <a>lexical space</a> of the datatype,
+and the second element belongs to the
+ <dfn>value space</dfn> of the datatype:
+</p>
+<ul>
+<li>
+Each member of the lexical space is paired with (maps to) exactly one member
+of the value space.
+</li>
+<li>
+Each member of the value space may be paired with any number (including
+zero) of members of the lexical space (lexical representations for that
+value).
+</li>
+</ul>
+
+<div class="note">
+<p>When the datatype is defined using XML Schema:
+</p>
+<ul>
+<li>
+All values correspond to some lexical form, either using
+the lexical-to-value mapping of the datatype or if it is a union
+datatype with a lexical mapping associated with one of the member
+datatypes.
+</li>
+<li>
+XML Schema facets remain part of the datatype and are used by the XML
+Schema mechanisms that control the lexical space and the value space;
+however, RDF does not define a standard mechanism to access these facets.</li>
+
+ <li>In [[XMLSCHEMA11-1]],
+ <a href="http://www.w3.org/TR/xmlschema11-1/#sec-wsnormalization">white space normalization</a>
+ occurs during
+ <a href="http://www.w3.org/TR/xmlschema11-1/#key-vn">validation</a>
+ according to the value of the
+ <a href="http://www.w3.org/TR/xmlschema11-2/#rf-whiteSpace">whiteSpace
+ facet</a>. The lexical-to-value mapping used in RDF datatyping
+ occurs after this, so that the whiteSpace facet has no
+ effect in RDF datatyping.</li>
+ </ul>
+ </div>
+
+ <p class="note"><a title="language-tagged string">Language-tagged
+ strings</a> have the <a>datatype IRI</a>
+ <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#langString</code>.
+ No datatype is formally defined for this IRI because the definition
+ of <a title="datatype">datatypes</a> does not accommodate
+ <a title="language tag">language tags</a> in the <a>lexical space</a>.
+ The <a>value space</a> associated with the datatype IRI is the set
+ of all pairs of strings and language tags.</p>
+
+ <p>For example, the XML Schema datatype <code>xsd:boolean</code>,
+ where each member of the <a>value space</a> has two lexical
+ representations, is defined as follows:</p>
+
+ <dl>
+ <dt>Lexical space:</dt>
+ <dd>{“<code>true</code>”, “<code>false</code>”, “<code>1</code>”, “<code>0</code>”}</dd>
+ <dt>Value space:</dt>
+ <dd>{<em><strong>true</strong></em>, <em><strong>false</strong></em>}</dd>
+ <dt>Lexical-to-value mapping</dt>
+ <dd>{
+ <“<code>true</code>”, <em><strong>true</strong></em>>,
+ <“<code>false</code>”, <em><strong>false</strong></em>>,
+ <“<code>1</code>”, <em><strong>true</strong></em>>,
+ <“<code>0</code>”, <em><strong>false</strong></em>>,
+ }</dd>
+ </dl>
+
+ <p>The <a title="literal">literals</a> that can be defined using this
+ datatype are:</p>
+
+ <table border="1" cellpadding="5" summary=
+ "This table lists the literals of type xsd:boolean.">
+ <tr>
+ <th>Literal</th>
+ <th>Value</th>
+ </tr>
+ <tr>
+ <td align="center"><“<code>true</code>”, <code>xsd:boolean</code>></td>
+ <td align="center"><em><strong>true</strong></em></td>
+ </tr>
+ <tr>
+ <td align="center"><“<code>false</code>”, <code>xsd:boolean</code>></td>
+ <td align="center"><em><strong>false</strong></em></td>
+ </tr>
+ <tr>
+ <td align="center"><“<code>1</code>”, <code>xsd:boolean</code>></td>
+ <td align="center"><em><strong>true</strong></em></td>
+ </tr>
+ <tr>
+ <td align="center"><“<code>0</code>”, <code>xsd:boolean</code>></td>
+ <td align="center"><em><strong>false</strong></em></td>
+ </tr>
+ </table>
+
+
+<section id="xsd-datatypes">
+ <h3>The XML Schema Built-in Datatypes</h3>
+
+ <p class="issue">XML Schema 1.1 added a number of new datatypes:
+ <code><a href="http://www.w3.org/TR/xmlschema11-2/#dateTimeStamp">xsd:dateTimeStamp</a></code>,
+ <code><a href="http://www.w3.org/TR/xmlschema11-2/#dayTimeDuration">xsd:dayTimeDuration</a></code>,
+ <code><a href="http://www.w3.org/TR/xmlschema11-2/#yearMonthDuration">xsd:yearMonthDuration</a></code>, and
+ <code><a href="http://www.w3.org/TR/xmlschema11-2/#precisionDecimal">xsd:precisionDecimal</a></code>.
+ Some of them are already used in RIF and OWL2. They should possibly be added
+ here as well. Also,
+ <code><a href="http://www.w3.org/TR/xmlschema11-2/#duration">xsd:duration</a></code>
+ is noted below as being unsuitable for use in RDF. The design of the type
+ has changed, so this should be reviewed. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/issues/66">ISSUE-66</a>.</p>
+
+ <p><a title="IRI">IRIs</a> of the form
+ <code>http://www.w3.org/2001/XMLSchema#<em>xxx</em></code>,
+ where <code><em>xxx</em></code>
+ is the name of a datatype, denote the built-in datatypes defined in
+ <em><a href="http://www.w3.org/TR/xmlschema11-2/">XML Schema 1.1 Part 2:
+ Datatypes</a></em> [[!XMLSCHEMA11-2]]. The XML Schema built-in types
+ listed in the following table are the
+ <dfn>RDF-compatible XSD types</dfn>. Their use is RECOMMENDED.</p>
+
+ <table class="xsd-types" rules="all">
+ <tr><th></th><th>Datatype</th><th>Value space (informative)</th></tr>
+
+ <tr><th rowspan="4">Core types</th><td><a href="http://www.w3.org/TR/xmlschema11-2/#string"><code>xsd:string</code></a></td><td>Character strings</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#boolean"><code>xsd:boolean</code></a></td><td>true, false</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#decimal"><code>xsd:decimal</code></a></td><td>Arbitrary-precision decimal numbers</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#integer"><code>xsd:integer</code></a></td><td>Arbitrary-size integer numbers</td></tr>
+
+ <tr><th rowspan="2">IEEE floating-point<br />numbers</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#double"><code>xsd:double</code></a></td><td>64-bit floating point numbers incl. ±Inf, ±0, NaN</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#float"><code>xsd:float</code></a></td><td>32-bit floating point numbers incl. ±Inf, ±0, NaN</td></tr>
+
+ <tr><th rowspan="3">Time and date</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#date"><code>xsd:date</code></a></td><td>Dates (yyyy-mm-dd) with or without timezone</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#time"><code>xsd:time</code></a></td><td>Times (hh:mm:ss.sss…) with or without timezone</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#dateTime"><code>xsd:dateTime</code></a></td><td>Date and time with or without timezone</td></tr>
+
+ <tr><th rowspan="5">Recurring and<br />partial dates</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#gYear"><code>xsd:gYear</code></a></td><td>Gregorian calendar year</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#gMonth"><code>xsd:gMonth</code></a></td><td>Gregorian calendar month</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#gDay"><code>xsd:gDay</code></a></td><td>Gregorian calendar day of the month</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#gYearMonth"><code>xsd:gYearMonth</code></a></td><td>Gregorian calendar year and month</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#gMonthDay"><code>xsd:gMonthDay</code></a></td><td>Gregorian calendar month and day</td></tr>
+
+ <tr><th rowspan="12">Limited-range<br />integer numbers</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#byte"><code>xsd:byte</code></a></td><td>-128…+127 (8 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#short"><code>xsd:short</code></a></td><td>-32768…+32767 (16 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#int"><code>xsd:int</code></a></td><td>-2147483648…+2147483647 (32 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#long"><code>xsd:long</code></a></td><td>-9223372036854775808…+9223372036854775807 (64 bit)</td></tr>
+
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#unsignedByte"><code>xsd:unsignedByte</code></a></td><td>0…255 (8 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#unsignedShort"><code>xsd:unsignedShort</code></a></td><td>0…65535 (16 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#unsignedInt"><code>xsd:unsignedInt</code></a></td><td>0…4294967295 (32 bit)</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#unsignedLong"><code>xsd:unsignedLong</code></a></td><td>0…18446744073709551615 (64 bit)</td></tr>
+
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#positiveInteger"><code>xsd:positiveInteger</code></a></td><td>Integer numbers >0</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#nonNegativeInteger"><code>xsd:nonNegativeInteger</code></a></td><td>Integer numbers ≥0</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#negativeInteger"><code>xsd:negativeInteger</code></a></td><td>Integer numbers <0</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#nonPositiveInteger"><code>xsd:nonPositiveInteger</code></a></td><td>Integer numbers ≤0</td></tr>
+
+ <tr><th rowspan="2">Encoded binary data</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#hexBinary"><code>xsd:hexBinary</code></a></td><td>Hex-encoded binary data</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#base64Binary"><code>xsd:base64Binary</code></a></td><td>Base64-encoded binary data</td></tr>
+
+ <tr><th rowspan="7">Miscellaneous<br />XSD types</th>
+ <td><a href="http://www.w3.org/TR/xmlschema11-2/#anyURI"><code>xsd:anyURI</code></a></td><td>Absolute or relative URIs and IRIs</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#language"><code>xsd:language</code></a></td><td>Language tags per [[BCP47]]</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#normalizedString"><code>xsd:normalizedString</code></a></td><td>Whitespace-normalized strings</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#token"><code>xsd:token</code></a></td><td>Tokenized strings</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#NMTOKEN"><code>xsd:NMTOKEN</code></a></td><td>XML NMTOKENs</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#Name"><code>xsd:Name</code></a></td><td>XML Names</td></tr>
+ <tr><td><a href="http://www.w3.org/TR/xmlschema11-2/#NCName"><code>xsd:NCName</code></a></td><td>XML NCNames</td></tr>
+ </table>
+
+ <p>The other built-in XML Schema datatypes are unsuitable
+ for various reasons, and SHOULD NOT be used.</p>
+
+ <div class="note">
+ <ul>
+ <li><a href="http://www.w3.org/TR/xmlschema11-2/#duration"><code>xsd:duration</code></a>
+ does not have a well-defined value space (this may be corrected
+ in later revisions of XML Schema datatypes, in which case the
+ revised datatype would be suitable for use in RDF datatyping).</li>
+ <li><a href="http://www.w3.org/TR/xmlschema11-2/#QName"><code>xsd:QName</code></a>
+ and
+ <a href="http://www.w3.org/TR/xmlschema11-2/#ENTITY"><code>xsd:ENTITY</code></a>
+ require an enclosing XML document context.</li>
+ <li><a href="http://www.w3.org/TR/xmlschema11-2/#ID"><code>xsd:ID</code></a>
+ and
+ <a href="http://www.w3.org/TR/xmlschema11-2/#IDREF"><code>xsd:IDREF</code></a>
+ are for cross references within an XML document.</li>
+ <li><a href="http://www.w3.org/TR/xmlschema11-2/#NOTATION"><code>xsd:NOTATION</code></a>
+ is not intended for direct use.</li>
+ <li><a href="http://www.w3.org/TR/xmlschema11-2/#IDREFS"><code>xsd:IDREFS</code></a>,
+ <a href="http://www.w3.org/TR/xmlschema11-2/#ENTITIES"><code>xsd:ENTITIES</code></a>
+ and
+ <a href="http://www.w3.org/TR/xmlschema11-2/#NMTOKENS"><code>xsd:NMTOKENS</code></a>
+ are sequence-valued datatypes which do not fit the RDF <a>datatype</a>
+ model.</li>
+ </ul>
+ </div>
+
+</section>
+
+
+<section id="section-XMLLiteral">
+ <h3>The <code>rdf:XMLLiteral</code> Datatype</h3>
+
+ <p class="issue">The canonicalization rules required for XML literals
+ are quite complicated. Increasingly, RDF is produced and consumed in
+ environments where no XML parser and canonicalization engine is
+ available. A possible change to relax the requirements for the
+ lexical space, while retaining the value space, is under discussion.
+ This is <a href="http://www.w3.org/2011/rdf-wg/track/issues/13">ISSUE-13</a>.</p>
+
+ <p>RDF provides for XML content as a possible <a>literal value</a>.
+ Such content is indicated in an <a>RDF graph</a> using a <a>literal</a>
+ whose <a>datatype</a> is a special built-in datatype
+ <code>rdf:XMLLiteral</code>.
+ This allows the inclusion of text that contains markup, such as
+ XHTML [[XHTML11]].</p>
+
+ <p class="issue">Should RDF define an HTML datatype? Arguably this would
+ be more useful for including markup in text. This is
+ <a href="http://www.w3.org/2011/rdf-wg/track/issues/63">ISSUE-63</a>.</p>
+
+ <p><code><dfn>rdf:XMLLiteral</dfn></code> is defined as follows.</p>
+
+ <dl>
+ <dt><a name="XMLLiteral-uri" id="XMLLiteral-uri">An IRI denoting
+ this datatype</a></dt>
+
+ <dd>is
+ <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>.</dd>
+
+ <dt><a name="XMLLiteral-lexical-space" id="XMLLiteral-lexical-space">The lexical space</a></dt>
+
+<dd>is the set of all
+strings:
+<ul>
+<li>which are well-balanced, self-contained
+<a href="http://www.w3.org/TR/2000/REC-xml-20001006#NT-content">
+XML content</a>
+[[!XML10]];
+</li>
+<li>for which encoding as UTF-8
+[[!UTF-8]] yields
+<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-exclusive-canonical-XML">
+exclusive
+Canonical XML </a> (with comments, with empty
+<a href="http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/#def-InclusiveNamespaces-PrefixList">
+InclusiveNamespaces PrefixList
+</a>) [[!XML-EXC-C14N]];
+</li>
+<li>for which embedding between an arbitrary XML start tag and an end tag
+yields a document conforming to <a href=
+ "http://www.w3.org/TR/1999/REC-xml-names-19990114/">XML
+ Namespaces</a> [[!XML-NAMES]]</li>
+</ul>
+</dd>
+
+
+ <dt><a name="XMLLiteral-value-space" id="XMLLiteral-value-space">The value space</a></dt>
+
+ <dd>is a set of entities, called XML values, which is:
+<ul>
+<li>disjoint from the lexical space;</li>
+<li>disjoint from the value space of any other datatype that is not explicitly defined as a sub- or supertype of this datatype;</li>
+<li>disjoint from the set of Unicode character strings [[!UNICODE]];</li>
+<li>and in 1:1 correspondence with the lexical space.</li>
+</ul>
+</dd>
+
+ <dt><a name="XMLLiteral-mapping" id="XMLLiteral-mapping">The lexical-to-value mapping</a></dt>
+
+ <dd>
+is a one-one mapping from the lexical space onto the value space,
+ i.e. it is both injective and surjective.
+</dd>
+
+
+
+ </dl>
+
+ <p class="note">Not all values of this datatype are compliant
+ with XML 1.1 [[XML11]]. If compliance
+ with XML 1.1 is desired, then only those values that are
+<a href="http://www.w3.org/TR/2002/CR-xml11-20021015/#sec2.13">fully
+ normalized</a> according to XML 1.1 should be used.</p>
+
+ <p class="note">XML values can be thought of as the
+[[XML-INFOSET]] or the [[XPATH]]
+nodeset corresponding to the lexical form, with an appropriate equality
+function.</p>
+
+ <p class="note">RDF applications may use additional equivalence relations,
+ such as that which relates an
+ <a href="http://www.w3.org/TR/xmlschema11-2/#string"><code>xsd:string</code></a>
+ with an <code>rdf:XMLLiteral</code> corresponding to a single text node
+ of the same string.</p>
+
+ <p class="note">If language annotation of XML literals is required,
+ it must be explicitly included as markup, usually by means of an
+ <code>xml:lang</code> attribute.</p>
+</section>
+
+<section id="datatype-maps">
+ <h3>Datatype Maps</h3>
+
+ <p>A <dfn>datatype map</dfn> is an implementation-defined set of
+ <<a>IRI</a>, <a>datatype</a>> pairs such that no
+ IRI appears twice in the set and the IRI denotes the datatype.
+ It can be seen as a function from IRIs
+ to datatypes. Every datatype map contains the pair
+ <<code>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral</code>,
+ <code><a>rdf:XMLLiteral</a></code>>.</p>
+
+ <p>The <dfn>XSD datatype map</dfn> is the <a>datatype map</a>
+ which also contains the set of all pairs of the form
+ <<code>http://www.w3.org/2001/XMLSchema#<em>xxx</em></code>,
+ <code>xsd:<em>xxx</em></code>>, where <code>xsd:<em>xxx</em></code>
+ is the name of an
+ <a title="RDF-compatible XSD types">RDF-compatible XSD type</a>.</p>
+
+</section>
+
+
+<section id="section-Literal-Value">
+ <h3>The Value Corresponding to a Literal</h3>
+
+ <p>The <dfn>literal value</dfn> associated with a <a>literal</a> is:</p>
+
+ <ol>
+ <li><strong>If the literal is a <a>language-tagged string</a>,</strong>
+ then the literal value is a pair consisting of its <a>lexical form</a>
+ and its <a>language tag</a>, in that order.</li>
+ <li><strong>If the literal's <a>datatype IRI</a> is not in the
+ <a>datatype map</a>,</strong> then the literal value is
+ not defined by this specification.</li>
+ <li>Let <em>d</em> be the <a>datatype</a> associated with the
+ datatype IRI in the datatype map.</li>
+ <li><strong>If the literal's <a>lexical form</a> is in the
+ <a>lexical space</a> of <em>d</em>,</strong> then the literal value
+ is the result of applying the <a>lexical-to-value mapping</a>
+ of <em>d</em> to the <a>lexical form</a>.</li>
+ <li><strong>Otherwise,</strong> the literal is
+ <dfn>ill-typed</dfn>, and no literal value can be
+ associated with the literal. Such a case, while in error, is not
+ <em>syntactically</em> ill-formed.</li>
+ </ol>
+
+ <p class="note">In application contexts, comparing the
+ <a title="literal value">values of literals</a> is usually
+ more helpful than comparing their syntactic forms
+ (<a>literal equality</a>).
+ Similarly, for comparing <a title="RDF graph">RDF Graphs</a>,
+ semantic notions of <a>entailment</a> are usually more helpful
+ than syntactic <a>graph equivalence</a>.</p>
+
+</section>
+
+
+</section>
+
+
<section id="section-multigraph">
<h2>Abstract Syntax for Working with Multiple Graphs</h2>
+ <p>The RDF data model expresses information as
+ <a title="RDF graph">RDF graphs</a> consisting of
+ <a title="triple">triples</a> with subject, predicate and object.
+ Often, one wants to hold multiple RDF graphs and record information
+ about each graph, allowing an application to work with datasets
+ that involve information from more than one graph.</p>
+
+ <p>An <dfn>RDF Dataset</dfn> is a collection of
+ <a title="RDF graph">RDF graphs</a> and comprises:</p>
+
+ <ul>
+ <li>Exactly one <dfn>default graph</dfn>, being an <a>RDF graph</a>.
+ The default graph does not have a name.</li>
+ <li>Zero or more <dfn title="named graph">named graphs</dfn>.
+ Each named graph is a pair consisting of an <a>IRI</a>
+ (the <dfn>graph name</dfn>), and an <a>RDF graph</a>.
+ Graph names are unique within an RDF dataset.</li>
+ </ul>
+
<div class="issue">
<p>The Working Group will standardize a model and semantics for
multiple graphs and graphs stores. The
@@ -1052,99 +1078,58 @@
<p>The design presented here should be considered a straw man proposal at this point. It is based on RDF Datasets as <a href="http://www.w3.org/TR/sparql11-query/#rdfDataset">defined in SPARQL 1.1</a>.</p>
</div>
- <p>The RDF data model expresses information as
- <a title="RDF graph">RDF graphs</a> consisting of
- <a title="triple">triples</a> with subject, predicate and object.
- Often, one wants to hold multiple RDF graphs and record information
- about each graph, allowing an application to work with datasets
- that involve information from more than one graph.</p>
-
- <p>An <dfn>RDF Dataset</dfn> is a collection of
- <a title="RDF graph">RDF graphs</a> and comprises:</p>
+ <p class="note">When graphs are merged, their blank nodes must be kept
+ distinct if meaning is to be preserved; this may call for re-allocation of
+ blank node identifiers.</p>
+ </div>
- <ul>
- <li>Exactly one <dfn>default graph</dfn>, being an <a>RDF graph</a>.
- The default graph does not have a name.</li>
- <li>Zero or more <dfn title="named graph">named graphs</dfn>.
- Each named graph is a pair consisting of an <a>IRI</a>
- (the <dfn>graph name</dfn>), and an <a>RDF graph</a>.
- Graph names are unique within an RDF dataset.</li>
- </ul>
-
-</section>
-
+ <p class="issue">Should “Graph merge” be defined in this spec?
+ If not, then the previous note could just as well go. This will be
+ decided once a multigraph design has been decided upon.</p>
</section>
<section id="section-fragID" class="informative">
<h2>Fragment Identifiers</h2>
- <p class="issue">This section does not address the case where RDF is
- embedded in other document formats, such as in RDFa or when an RDF/XML
- fragment is embedded in SVG. It has been suggested that this may be
- a general issue for the TAG about the treatment of
- fragment identifiers when one language is embedded in another. This is
- <a href="http://www.w3.org/2011/rdf-wg/track/issues/37">ISSUE-37</a>.</p>
-
- <p class="issue">This section treats the RDF/XML media type as
- canonical for establishing the referent of IRIs that include
- fragment identifier. Today we have many different media types
- that can carry RDF graphs, and HTTP content negotiation is more
- common. Also, the problem addressed in the section
- (context-dependence of fragment identifiers) has to some extent
- gone away when RFC 2396 was replaced by RFC 3986. The latter
- states that the same fragment should be used for the same thing
- in resources that have multiple representations
- (Section 3.5 [[URI]]). This is
- <a href="http://www.w3.org/2011/rdf-wg/track/issues/69">ISSUE-69</a>.</p>
+ <p>RDF uses <a title="IRI">IRIs</a>, which may include
+ <dfn>fragment identifiers</dfn>, as resource identifiers.
+ The semantics of fragment identifiers are
+ <a href="http://tools.ietf.org/html/rfc3986#section-3.5">defined in
+ RFC 3986</a> [[URI]]: They identify a secondary resource
+ that is usually a part of, view of, defined in, or described in
+ the primary resource, and the precise semantics depend on the set
+ of representations that might result from a retrieval action
+ on the primary resource.</p>
- <p>RDF uses <a title="IRI">IRIs</a>,
- which may include fragment identifiers, as
- context free identifiers for resources. RFC 2396 states
- that the meaning of a fragment
- identifier depends on the MIME content-type of a document, i.e.
- is context dependent.</p>
- <p>These apparently conflicting views are reconciled by
- considering that an <a>IRI</a> in an RDF graph is treated
- with respect to the MIME type <code>application/rdf+xml</code>
- [[RDF-MIME-TYPE]]. Given an IRI that includes a fragment identifier,
- the fragment identifer identifies the same thing
- that it does in an <code>application/rdf+xml</code> representation of the
- resource identified by the IRI excluding the fragment identifier. Thus:</p>
- <ul>
- <li>we assume that the IRI excluding fragment
- identifier identifies a resource, which is presumed to have
- an RDF representation. So when <code>eg:someurl#frag</code> is used in an RDF
- document, <code>eg:someurl</code> is taken to
- designate some RDF document (even when no such document can
- be retrieved).</li>
- <li><code>eg:someurl#frag</code> means the thing
- that is indicated, according to the rules of the
- <code>application/rdf+xml</code> MIME content-type as
- a “fragment” or “view” of the RDF document at
- <code>eg:someurl</code>. If the document does not
- exist, or cannot be retrieved, or is available only in
- formats other than <code>application/rdf+xml</code>, then exactly what
- that view may be is somewhat undetermined, but that does not
- prevent use of RDF to say things about it.</li>
- <li>the RDF treatment of a fragment identifier allows it to
- indicate a thing that is entirely external to the document,
- or even to the “shared information space” known as the Web.
- That is, it can be a more general idea, like some particular
- car or a mythical Unicorn.</li>
- <li>in this way, an <code>application/rdf+xml</code> document acts as an
- intermediary between some Web retrievable documents (itself,
- at least, also any other Web retrievable IRIs that it may
- use, possibly including schema IRIs and references to other
- RDF documents), and some set of possibly abstract or non-Web
- entities that the RDF may describe.</li>
- </ul>
- <p>This provides a handling of IRIs and their
- denotation that is consistent with the RDF model theory and
- usage, and also with conventional Web behavior. Note that
- nothing here requires that an RDF application be able to
- retrieve any representation of resources identified by the IRIs
- in an RDF graph.</p>
+ <p>This section discusses the handling of fragment identifiers
+ in representations that encode <a title="RDF graph">RDF graphs</a>.</p>
+
+ <p>In RDF-bearing representations of a resource <code><foo></code>,
+ the secondary resource identified by a fragment <code>#bar</code>
+ is the entity denoted by the full IRI <code><foo#bar></code>
+ in the RDF graph.
+ Since IRIs in RDF graphs can denote anything, this can be
+ something external to the representation, or even external
+ to the Web.</p>
+
+ <p>In this way, the RDF representation acts as an intermediary
+ between some web-retrievable document, and some set of possibly
+ non-web or abstract entities that the RDF may describe.</p>
+
+ <p>Primary resources may have multiple representations
+ (a.k.a. content negotiation). Fragments in RDF-bearing representations
+ SHOULD be used consistently with the semantics imposed by any
+ non-RDF representations. For example, if the fragment
+ <code>#chapter1</code> identifies a document section in an
+ HTML representation of a primary resource, then <code>#chapter1</code>
+ SHOULD be taken to denote that same section in all RDF-bearing
+ representations of the same primary resource.</p>
+
+ <p>Likewise, RDF graphs embedded in non-RDF representations
+ with mechanism such as RDFa [[RDFA-PRIMER]]
+ should use fragment identifiers consistently with the semantics
+ imposed by the host language.</p>
</section>
@@ -1176,9 +1161,16 @@
<h2>Changes from RDF 2004</h2>
<ul>
+ <li>2011-11-21: Updated XHTML 1.0 reference to XHTML 1.1</li>
+ <li>2011-11-20: Added table of <a>RDF-compatible XSD types</a>, and definition of <a>datatype map</a>, both adapted from previous content in [[RDF-MT]]
+ <li>2011-11-18: Replaced informative <em>Introduction</em> and <em>RDF Concepts</em> sections with a new extended introduction. Folded some content from <em>RDF Concepts</em> into the later normative sections, mostly as examples and notes.</li>
+ <li>2011-11-10: Changed XSD references to version 1.1</li>
+ <li>2011-11-10: Replaced the <a href="#section-fragID">section on fragment identifiers</a> with an updated account that follows RFC 3986</li>
+ <li>2011-11-09: Updated the two sections on literals to reflect the <a href="http://www.w3.org/2011/rdf-wg/track/issues/71">ISSUE-71</a> resolution that literals with language tag now have the datatype IRI <code>rdf:langString</code>. Formally introduced the term “language-tagged string”.</li>
+ <li>2011-11-09: Add a note that explains that #x0-#x1F are no longer allowed in simple literals
<li>2011-08-13: Updated Turtle reference to Turtle FPWD</li>
<li>2011-07-21: Condensed the 2004 acknowledgements</li>
- <li>2011-07-21: Updated the two sections on literals to reflect the <a href="">ISSUE-12 resolution</a> that simple literals are no longer part of the abstract syntax. Formally introduced the terms “language-tagged literal”, “simple literal”.</li>
+ <li>2011-07-21: Updated the two sections on literals to reflect the <a href="http://www.w3.org/2011/rdf-wg/track/issues/12">ISSUE-12</a> resolution that simple literals are no longer part of the abstract syntax. Formally introduced the terms “language-tagged literal”, “simple literal”.</li>
<li>2011-07-21: Updated the introduction, and removed many mentions of RDF/XML. Changed the normative reference for the terms in the RDF namespace from the RDF/XML spec to the RDF Schema spec. Removed any mention of the 1999 version of RDF.</li>
<li>2011-07-21: Replaced RFC 2279 reference (UTF-8) with RFC 3629</li>
<li>2011-07-20: Removed informative sections “Motivations and Goals” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-Overview">RDF 2004 version</a>) and “RDF Expression of Simple Facts” (see <a href="http://www.w3.org/TR/rdf-concepts/#section-SimpleFacts">RDF 2004 version</a>)</li>
@@ -1195,7 +1187,13 @@
</section>
-<section id="references"></section>
+<section id="references">
+ <p class="issue">This specification normatively references version 1.1
+ of XML Schema [[XMLSCHEMA11-1]] and [[XMLSCHEMA11-2]].
+ These documents have not yet reached W3C Recommendation status,
+ but are expected to do so before <em>RDF 1.1 Concepts and
+ Abstract Syntax</em> goes to Last Call.</p>
+</section>
</body>
</html>