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    <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src=
    "http://www.w3.org/Icons/w3c_home" width="72"></a></p>

    <h1>HTML+RDFa</h1>

    <h2 class="no-num no-toc" id="a-mechanism-for-embedding-rdf-in-html">A
    mechanism for embedding RDF in HTML</h2>

    <h2 class="no-num no-toc" id="editor-s-draft-date-13-October-2009">W3C
    Working Draft 15 October 2009</h2><!--:ZZZ-->

    <dl>
      <!-- ZZZ: update the month/day (twice), (un)comment out
    <dt>This Version:</dt>
    <dd><a href="http://www.w3.org/TR/2009/WD-html5-20090423/">http://www.w3.org/TR/2009/WD-html5-20090423/</a></dd>
 :ZZZ -->

      <dt>This Version</dt>

      <dd><a href=
      "http://www.w3.org/TR/2009/WD-rdfa-in-html-20091015/">http://www.w3.org/TR/2009/WD-rdfa-in-html-20091015/</a></dd>

      <dt>Latest Version</dt>

      <dd><a href=
      "http://www.w3.org/TR/rdfa-in-html/">http://www.w3.org/TR/rdfa-in-html/</a></dd>

      <dt>Authors (alphabetical order):</dt>

      <dd>Ben Adida (Chair, RDFa Task Force, Creative Commons)</dd>

      <dd>Mark Birbeck (Editor, XHTML+RDFa and inventor of RDFa concept, Web
      Backplane Ltd.)</dd>

      <dd>Shane McCarron (Editor, XHTML+RDFa, Applied Testing and Technology,
      Inc.)</dd>

      <dd>Steven Pemberton (Chair, XHTML2 and RDFa Task Force member,
      CWI)</dd>

      <dd><a href="mailto:msporny@digitalbazaar.com">Manu Sporny</a>,
      (Editor, HTML+RDFa and RDFa Task Force member, Digital Bazaar,
      Inc.)</dd>
    </dl>

    <p class="copyright"><a href=
    "http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
    &copy; 2009 <a href="http://www.w3.org/"><abbr title=
    "World Wide Web Consortium">W3C</abbr></a><sup>&reg;</sup> (<a href=
    "http://www.csail.mit.edu/"><abbr title=
    "Massachusetts Institute of Technology">MIT</abbr></a>, <a href=
    "http://www.ercim.org/"><abbr title=
    "European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
    <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
    <a href=
    "http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
    <a href=
    "http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
    and <a href=
    "http://www.w3.org/Consortium/Legal/copyright-documents">document use</a>
    rules apply.</p>
  </div>
  <hr class="top">

  <h2 class="no-num no-toc" id="abstract">Abstract</h2>

  <p>This specification defines rules and guidelines for adapting the RDF in
  XHTML: Syntax and Processing (RDFa) specification for use in the HTML5 and
  XHTML5 members of the HTML family. The rules defined in this document not
  only apply to HTML5 documents in non-XML and XML mode, but also to HTML4
  documents interpreted through the HTML5 parsing rules.</p>

  <h2 class="no-num no-toc" id="status-of-this-document">Status of this
  document</h2><!-- intro boilerplate (required) -->

  <p><em>This section describes the status of this document at the time of
  its publication. Other documents may supersede this document. A list of
  current W3C publications and the latest revision of this technical report
  can be found in the <a href="http://www.w3.org/TR/">W3C technical reports
  index</a> at http://www.w3.org/TR/.</em></p>

  <p>This is the First Public Working Draft of the "HTML+RDFa: A mechanism
  for embedding RDF in HTML" specification for review by W3C members and
  other interested parties.</p>

  <p>If you wish to make comments regarding this document, please send them
  to <a href=
  "mailto:public-rdf-in-xhtml-tf@w3.org">public-rdf-in-xhtml-tf@w3.org</a>
  (<a href=
  "mailto:public-rdf-in-xhtml-tf-request@w3.org?subject=subscribe">subscribe</a>,
  <a href=
  "http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/">archives</a>)
  or to <a href=
  "mailto:public-html-comments@w3.org">public-html-comments@w3.org</a>
  (<a href=
  "mailto:public-html-comments-request@w3.org?subject=subscribe">subscribe</a>,
  <a href=
  "http://lists.w3.org/Archives/Public/public-html-comments/">archives</a>),
  or submit them using the <a href=
  "http://www.w3.org/Bugs/Public/enter_bug.cgi">W3C's public bug
  database</a>.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- stability (required) -->

  <p>Implementors should be aware that this specification is not stable.
  <strong>Implementors who are not taking part in the discussions are likely
  to find the specification changing out from under them in incompatible
  ways.</strong> Vendors interested in implementing this specification before
  it eventually reaches the Candidate Recommendation stage should join the
  aforementioned mailing lists and take part in the discussions.</p>
  <!-- not everyone agrees with html5 (requested before fpwd) -->

  <p>Publication as a Working Draft does not imply endorsement by the W3C
  Membership. This is a draft document and may be updated, replaced or
  obsoleted by other documents at any time. It is inappropriate to cite this
  document as other than work in progress.</p>

  <p>The publication of this document by the W3C as a W3C Working Draft does
  not imply that all of the participants in the W3C HTML working group
  endorse the contents of the specification. Indeed, for any section of the
  specification, one can usually find many members of the working group or of
  the W3C as a whole who object strongly to the current text, the existence
  of the section at all, or the idea that the working group should even spend
  time discussing the concept of that section.</p>
  <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) -->

  <p>The latest stable version of the editor's draft of this specification is
  always available on <a href="http://dev.w3.org/html5/rdfa/">the W3C CVS
  server</a>. The <a href=
  "http://html5.digitalbazaar.com/specs/rdfa.html">latest editor's working
  copy</a> (which may contain unfinished text in the process of being
  prepared) is also available.</p>
  <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) -->

  <p>The W3C <a href="http://www.w3.org/html/wg/">HTML Working Group</a> is
  the W3C working group responsible for this specification's progress along
  the W3C Recommendation track.</p>
  <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) -->

  <p>This specification is an extension to the HTML5 language. All normative
  content in the HTML5 specification, unless specifically overridden by this
  specification, is intended to be the basis for this specification.</p>
  <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate -->

  <p>This document was produced by a group operating under the <a href=
  "http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C
  Patent Policy</a>. W3C maintains a <a href=
  "http://www.w3.org/2004/01/pp-impl/40318/status" rel="disclosure">public
  list of any patent disclosures</a> made in connection with the deliverables
  of the group; that page also includes instructions for disclosing a patent.
  An individual who has actual knowledge of a patent which the individual
  believes contains <a href=
  "http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
  Claim(s)</a> must disclose the information in accordance with <a href=
  "http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
  6 of the W3C Patent Policy</a>.</p>

  <h2 class="no-num no-toc" id="contents">Table of contents</h2>
  <!--begin-toc-->

  <ol class="toc">
    <li>
      <a href="#introduction"><span class="secno">1</span> Introduction</a>

      <ol>
        <li><a href="#history"><span class="secno">1.1</span>
        History</a></li>
      </ol>
    </li>

    <li>
      <a href="#parsing-model"><span class="secno">2</span> Parsing Model</a>

      <ol>
        <li><a href="#modifying-the-input-document"><span class=
        "secno">2.1</span> Modifying the Input Document</a></li>
      </ol>
    </li>

    <li>
      <a href="#conformance-requirements"><span class="secno">3</span>
      Conformance Requirements</a>

      <ol>
        <li><a href="#document-conformance"><span class="secno">3.1</span>
        Document Conformance</a></li>

        <li><a href="#user-agent-conformance"><span class="secno">3.2</span>
        User Agent Conformance</a></li>

        <li><a href="#rdfa-processor-conformance"><span class=
        "secno">3.3</span> RDFa Processor Conformance</a></li>
      </ol>
    </li>

    <li>
      <a href="#modifications-to-xhtml-rdfa"><span class="secno">4</span>
      Modifications to XHTML+RDFa</a>

      <ol>
        <li><a href="#specifying-the-language-for-a-literal"><span class=
        "secno">4.1</span> Specifying the language for a literal</a></li>

        <li><a href="#invalid-xmlliteral-values"><span class=
        "secno">4.2</span> Invalid XMLLiteral values</a></li>

        <li><a href="#xmlns:-prefixed-attributes"><span class=
        "secno">4.3</span> <code>xmlns:</code>-Prefixed Attributes</a></li>
      </ol>
    </li>

    <li>
      <a href="#extensions-to-the-html5-syntax"><span class="secno">5</span>
      Extensions to the HTML5 Syntax</a>

      <ol>
        <li><a href="#the-rdfa-attributes-and-valid-values"><span class=
        "secno">5.1</span> The RDFa Attributes and Valid Values</a></li>

        <li><a href=
        "#conformance-criteria-for-xmlns:-prefixed-attributes"><span class=
        "secno">5.2</span> Conformance Criteria for
        <code>xmlns:</code>-Prefixed Attributes</a></li>
      </ol>
    </li>

    <li>
      <a href="#references"><span class="secno">6</span> References</a>

      <ol>
        <li><a href="#normative-references"><span class="secno">6.1</span>
        Normative References</a></li>

        <li><a href="#non-normative-references"><span class=
        "secno">6.2</span> Non-Normative References</a></li>
      </ol>
    </li>
  </ol><!--end-toc-->
  <hr>

  <h2 id="introduction"><span class="secno">1</span> Introduction</h2>

  <p class="XXX annotation"><b>Status:</b> <i>Working draft</i></p>

  <p><em>This section is informative.</em></p>

  <p>Today's web is built predominantly for human consumption. Even as
  machine-readable data begins to permeate the web, it is typically
  distributed in a separate file, with a separate format, and very limited
  correspondence between the human and machine versions. As a result, web
  browsers can provide only minimal assistance to humans in parsing and
  processing web data: browsers only see presentation information. RDFa is
  intended to solve the problem of machine-readable data in HTML documents.
  RDFa provides a set of HTML attributes to augment visual data with
  machine-readable hints. Using RDFa, authors may turn their existing
  human-visible text and links into machine-readable data without repeating
  content.</p>

  <h3 id="history"><span class="secno">1.1</span> History</h3>

  <p class="XXX annotation"><b>Status:</b> <i>Working draft</i></p>

  <p>In early 2004, Mark Birbeck published a document named [<a href=
  "#refsXHTMLRDF">XHTMLRDF</a>] via the XHTML2 Working Group wherein he laid
  the groundwork for what would eventually become RDFa (The Resource
  Description Framework in Attributes).</p>

  <p>In 2006, the work was co-sponsored by the Semantic Web Deployment Work
  Group, which began to formalize a technology to express semantic data in
  XHTML. This technology was successfully developed and reached consensus at
  the W3C, later published as an official W3C Recommendation. While HTML
  provides a mechanism to express the structure of a document (title,
  paragraphs, links), RDFa provides a mechanism to express the meaning in a
  document (people, places, events).</p>

  <p>The document, titled "RDF in XHTML: Syntax and Processing" [<a href=
  "#refsXHTMLRDFA">XHTML+RDFa</a>], defined a set of attributes and rules for
  processing those attributes that resulted in the output of machine-readable
  semantic data. While the document applied to XHTML, the attributes and
  rules were always intended to operate across any tree-based structure
  containing attributes on tree nodes (such as HTML4, SVG and ODF).</p>

  <p>While RDFa was initially specified for use in XHTML, adoption by a
  number of large organizations on the Web spurred RDFa's use in non-XHTML
  languages. Its use in HTML4, before an official specification was developed
  for those languages, caused concern regarding document conformance.</p>

  <p>Over the years, the members of the RDFa Task Force [<a href=
  "http://rdfa.info/">RDFaTF</a>] had discussed the possibility of applying
  the same attributes and processing rules outlined in the XHTML+RDFa
  specification to all HTML family documents. By design, the possibility of a
  unified semantic data expression mechanism between all HTML and XHTML
  family documents was squarely in the realm of possibility.</p>

  <p>This section describes the modifications to the original XHTML+RDFa
  specification that permit the use of RDFa in all HTML family documents. By
  using the attributes and processing rules described in the XHTML+RDFa
  specification and heeding the minor changes in this section, authors can
  expect to generate markup that produces the same semantic data output in
  HTML4, HTML5 and XHTML5.</p>

  <h2 id="parsing-model"><span class="secno">2</span> Parsing Model</h2>

  <p><em>This section is normative.</em></p>

  <p><a href="http://www.w3.org/TR/rdfa-syntax/#sec_5.5.">Section 5.5:
  Sequence</a>, of the [<a href=
  "http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFa</a>] specification defines a
  generic processing model for extracting RDF from a tree-based model. The
  method of transforming an input document into a model suited for the RDFa
  processing rules is intentionally not defined in the XHTML+RDFa
  specification. The method of transformation was intended to be defined in
  the implementation language, in this case, this section of the HTML+RDFa
  specification.</p>

  <p>The HTML5 and XHTML5 DOMs are each a super-set of the tree-based model
  on which the RDFa processing rules operate. Therefore, a mapping mechanism
  to translate from a DOM to a tree-model is not necessary. The HTML5 and
  XHTML5 DOM, or equivalent data structure, should be used as input to the
  RDFa processing rules. The normative language for construction of the HTML5
  DOM and XHTML5 DOM is contained in the HTML5 specification.</p>

  <h3 id="modifying-the-input-document"><span class="secno">2.1</span>
  Modifying the Input Document</h3>

  <p><em>This section is informative.</em></p>

  <p>RDFa's tree-based processing rules, outlined in <a href=
  "http://www.w3.org/TR/rdfa-syntax/#sec_5.5.">Section 5.5: Sequence</a> of
  the XHTML+RDFa specification, allow an input document to be automatically
  corrected, cleaned-up, re-arranged, or modified in any way that is approved
  by the host language prior to processing. For example, element nesting
  issues in HTML documents may be corrected before the input document is
  translated into the DOM, a valid tree-based model, on which the RDFa
  processing rules will operate.</p>

  <p>Any mechanism that generates a data structure equivalent to the HTML5 or
  XHTML5 DOM, such as the html5lib library, may be used as the mechanism to
  construct the tree-based model provided as input to the RDFa processing
  rules.</p>

  <h2 id="conformance-requirements"><span class="secno">3</span> Conformance
  Requirements</h2>

  <p class="XXX annotation"><b>Status:</b> <i>Working draft</i></p>

  <p><em>This section is normative.</em></p>

  <p>The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
  interpreted as described in [<a class="nref" href=
  "#refsRFC2119">RFC2119</a>].</p>

  <h3 id="document-conformance"><span class="secno">3.1</span> Document
  Conformance</h3>

  <p>In order for a document to claim that it is a conforming HTML+RDFa
  document, it must provide the facilities described as mandatory in this
  section. The document conformance criteria are listed below, of which only
  a subset are mandatory:</p>

  <ol>
    <li>All document conformance requirements stated as mandatory in the
    HTML5 specification must be met.</li>

    <li>There should be a <code>version</code> attribute on the
    <code>html</code> element. The value of the <code>version</code>
    attribute should be "HTML+RDFa 1.0" if the document is a non-XML mode
    document, or "XHTML+RDFa 1.0" if the document is a XML mode
    document.</li>

    <li>There may be a <code>link</code> element contained in the
    <code>head</code> element that contains <code>profile</code> for the the
    <code>rel</code> attribute and
    <code>http://www.w3.org/1999/xhtml/vocab</code> for the <code>href</code>
    attribute.</li>
  </ol>

  <h3 id="user-agent-conformance"><span class="secno">3.2</span> User Agent
  Conformance</h3>

  <p>A conforming RDFa user agent must:</p>

  <ul>
    <li>Conform to all requirements listed in the <span>Conformance
    requirements</span> section of the HTML5 specification.</li>

    <li>Implement all of the features required by this specification.</li>

    <li>Implement all of the features specified in the XHTML+RDFa
    specification, excluding those features which are specifically overridden
    by this specification as detailed in the <a href=
    "#modifications-to-xhtml-rdfa">Modifications to XHTML+RDFa</a>.</li>
  </ul>

  <h3 id="rdfa-processor-conformance"><span class="secno">3.3</span> RDFa
  Processor Conformance</h3>

  <p>A conforming RDFa Processor must implement all of the mandatory features
  specified in the XHTML+RDFa specification. It must also support any
  mandatory features specified in this specification.</p>

  <h2 id="modifications-to-xhtml-rdfa"><span class="secno">4</span>
  Modifications to XHTML+RDFa</h2>

  <p><em>This section is normative.</em></p>

  <p>The [<a href="http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFa</a>]
  Recommendation is the base document on which this specification builds.
  XHTML+RDFa specifies the attributes, in <a href=
  "http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes">Section 2.1: The RDFa
  Attributes</a>, and processing model, in <a href=
  "http://www.w3.org/TR/rdfa-syntax/#s_model">Section 5: Processing
  Model</a>, for extracting RDF from an XHTML document. This section
  specifies changes to the attributes and processing model defined in
  XHTML+RDFa in order to support extracting RDF from HTML documents.</p>

  <p>The requirements and rules, as specified in XHTML+RDFa and further
  modified in this document, apply to all HTML5 documents. The RDFa Processor
  operating on HTML and XHTML documents, specifically the resulting DOMs,
  must apply the same processing rules for both types of serializations and
  DOMs.</p>

  <h3 id="specifying-the-language-for-a-literal"><span class=
  "secno">4.1</span> Specifying the language for a literal</h3>

  <p>The <code>lang</code> attribute must be processed in the same manner as
  the <code>xml:lang</code> attribute is in the XHTML+RDFa specification,
  <a href="http://www.w3.org/TR/rdfa-syntax/#sec_5.5.">Section 5.5:
  Sequence</a>, step #3.</p>The rules for determining the language of a node
  are specified in the section titled <a href=
  "http://www.w3.org/TR/html5/Overview.html#the-lang-and-xml:lang-attributes">
  The lang and xml:lang attributes</a> in the HTML5 specification.

  <p>If an author is editing an HTML fragment and is unsure of the final
  encapsulating MIME type for their markup, it is suggested that the author
  specify both <code>lang</code> and <code>xml:lang</code> where the value in
  both attributes is exactly the same.</p>

  <h3 id="invalid-xmlliteral-values"><span class="secno">4.2</span> Invalid
  XMLLiteral values</h3>

  <p>When generating literals of type XMLLiteral, the processor must ensure
  that the output XMLLiteral is a namespace well-formed XML fragment. A
  namespace well-formed XML fragment has the following properties:</p>

  <ul>
    <li>The XML fragment, when placed inside of a single root element, must
    validate as well-formed XML. The normative language that describes a
    well-formed XML document is specified in <a href=
    "http://www.w3.org/TR/REC-xml/#sec-well-formed">Section 2.1 "Well-Formed
    XML Documents"</a> of the XML specification.</li>

    <li>A case-insensitive match for the currently active <code>xmlns</code>
    attribute as well as all currently active attributes starting with
    <code>xmlns:</code> must be preserved in the generated XMLLiteral. This
    preservation must be accomplished by placing all active namespaces in
    each top-level element in the generated XMLLiteral, taking care to not
    over-write pre-existing namespace values.</li>
  </ul>If the input is not a namespace well-formed XML fragment, the
  processor must transform the input text in a way that ensures the
  well-formedness rules described in this section. If a sequence of
  characters cannot be transformed into a namespace well-formed XML fragment,
  the triple containing the XMLLiteral must not be generated.

  <p>An RDFa Processor that transforms the XML fragment must use the <a href=
  "http://www.w3.org/TR/html5/Overview.html#coercing-an-html-dom-into-an-infoset">
  Coercing an HTML DOM into an Infoset</a> rules, as specified in the HTML5
  specification, prior to generating the triple containing the XMLLiteral.
  The serialization algorithm that must be used for generating the XMLLiteral
  is normatively defined in the <a href=
  "http://www.w3.org/TR/html5/Overview.html#serializing-xhtml-fragments">Serializing
  XHTML Fragments</a> section of the HTML5 specification.</p>

  <p>Transformation to a namespace well-formed XML fragment is required
  because an application that consumes XMLLiteral data expects that data to
  be a namespace well-formed XML fragment.</p>

  <p>The transformation requirement does not apply to input data that are
  text-only, such as literals that contain a <code>datatype</code> attribute
  with an empty value (<code>""</code>), or input data that that contain only
  text nodes.</p>

  <p>An example transformation demonstrating the preservation of namespace
  values is provided below. The &rarr; symbol is used to denote that the line
  is a continuation of the previous line and is included purely for the
  purposes of readability:</p>
  <pre>
&lt;p xmlns:ex="http://example.org/vocab#"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"&gt;
 Two rectangles (the example markup for them are stored in a triple):
 &lt;svg xmlns="http://www.w3.org/2000/svg" property="ex:markup" datatype="rdf:XMLLiteral"&gt;
&rarr; &lt;rect width="300" height="100"
&rarr; style="fill:rgb(0,0,255);stroke-width:1; stroke:rgb(0,0,0)"/&gt;
&rarr; &lt;rect width="50" height="50"
&rarr; style="fill:rgb(255,0,0);stroke-width:2;
&rarr; stroke:rgb(0,0,0)"/&gt;&lt;/svg&gt;
&lt;/p&gt;

</pre>The markup above should produce the following triple:
  <pre>
&lt;&gt;
   &lt;http://example.org/vocab#markup&gt;
      "&lt;rect xmlns=\"http://www.w3.org/2000/svg\" width=\"300\"
&rarr; height=\"100\" style=\"fill:rgb(0,0,255);stroke-width:1; stroke:rgb(0,0,0)\"/&gt;
&rarr; &lt;rect xmlns=\"http://www.w3.org/2000/svg\" width=\"50\"
&rarr; height=\"50\" style=\"fill:rgb(255,0,0);stroke-width:2;
&rarr; stroke:rgb(0,0,0)\"/&gt;"^^http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral

</pre>Note the preservation of the SVG namespace by injecting a new
<code>xmlns</code> attribute. Since the <code>ex</code> and <code>rdf</code>
namespaces are not used in either <code>rect</code> element, they are not
preserved in the XMLLiteral.

  <h3 id="xmlns:-prefixed-attributes"><span class="secno">4.3</span>
  <code>xmlns:</code>-Prefixed Attributes</h3>

  <p class="XXX">While this section outlines xmlns: processing in RDFa, the
  support for distributed extensibility in non-XML mode HTML5 (using xmlns
  and xmlns:) is still an open issue. This section may be further modified
  before Last Call based on progress made on the distributed extensibility
  issue.</p>

  <p>CURIE prefix mappings specified using attributes prepended with
  <code>xmlns:</code> must be processed using the rules specified in <a href=
  "">Section 5.4, CURIE and URI Processing,</a> contained in the XHTML+RDFa
  specification.</p>

  <p>Since CURIE prefix mappings have been specified using
  <code>xmlns:</code>, and since HTML attribute names are case-insensitive,
  CURIE prefix names declared using the <code>xmlns:</code>attribute-name
  pattern <code>xmlns:&lt;PREFIX&gt;="&lt;URI&gt;"</code> should be specified
  using only lower-case characters. For example, the text
  "<code>xmlns:</code>" and the text in <code>"&lt;PREFIX&gt;"</code> should
  be lower-case only. This is to ensure that prefix mappings are interpreted
  in the same way between HTML (case-insensitive attribute names) and XHTML
  (case-sensitive attribute names) document types.</p>

  <h2 id="extensions-to-the-html5-syntax"><span class="secno">5</span>
  Extensions to the HTML5 Syntax</h2>

  <p><em>This section is normative.</em></p>

  <p>There are a few changes that are required to the HTML5 specification in
  order to fully support RDFa. The following sub-sections outline the
  necessary modifications to the base HTML5 specification.</p>

  <h3 id="the-rdfa-attributes-and-valid-values"><span class=
  "secno">5.1</span> The RDFa Attributes and Valid Values</h3>

  <p>All RDFa attributes and valid values (including CURIEs), as listed in
  <a href="http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes">Section 2.1:
  The RDFa Attributes</a>, are conforming when used in an HTML5 or XHTML5
  document.</p>

  <h3 id="conformance-criteria-for-xmlns:-prefixed-attributes"><span class=
  "secno">5.2</span> Conformance Criteria for <code>xmlns:</code>-Prefixed
  Attributes</h3>

  <p class="XXX">While this section outlines xmlns: conformance criteria for
  HTML+RDFa, the support for distributed extensibility in non-XML mode HTML5
  (using xmlns and xmlns:) is still an open issue. This section may be
  further modified before Last Call based on progress made on the distributed
  extensibility issue.</p>

  <p>Since RDFa uses attributes starting with <code>xmlns:</code> to specify
  CURIE prefixes, it is important that any attribute starting with a
  case-insensitive match on the text string "<code>xmlns:</code>" be
  preserved in the DOM or other tree-like model that is passed to the RDFa
  Processor. While it is specified that HTML5 must preserve these attributes
  in the DOM, it must also accept these attributes as conforming in non-XML
  HTML5. For documents conforming to this specification, attributes with
  names that have the case insensitive prefix "<code>xmlns:</code>" are
  conforming in both HTML5 and XHTML5.</p>

  <h2 id="references"><span class="secno">6</span> References</h2>

  <p class="XXX annotation"><b>Status:</b> <i>First draft</i></p>

  <h3 id="normative-references"><span class="secno">6.1</span> Normative
  References</h3>

  <dl>
    <dt id="refsHTML5">[<a href="http://www.w3.org/TR/html5/">HTML5</a>]
    (currently not a REC)</dt>

    <dd>The HTML5 Specification, Ian Hickson. W3C, Work in Progress</dd>

    <dt id="refsRFC2119">[<a href=
    "http://www.ietf.org/rfc/rfc2119.txt">RFC2119</a>]</dt>

    <dd>RFC2119: Key words for use in RFCs to Indicate Requirement Levels, S.
    Bradner. IETF, March 1997.</dd>

    <dt id="refsXHTMLRDFA">[<a href=
    "http://www.w3.org/TR/rdfa-syntax/">XHTML+RDFA</a>]</dt>

    <dd>RDFa in XHTML: Syntax and Processing, Mark Birbeck, Shane McCarron,
    Steven Pemberton. W3C, October 2008.</dd>
  </dl>

  <h3 id="non-normative-references"><span class="secno">6.2</span>
  Non-Normative References</h3>

  <dl>
    <dt id="refsXHTMLRDF">[<a href=
    "http://www.w3.org/MarkUp/2004/02/xhtml-rdf.html">XHTMLRDF</a>]</dt>

    <dd>XHTML and RDF, Mark Birbeck. W3C, February 2008.</dd>
  </dl>
</body>
</html>