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<title>Microdata to RDF</title>
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/* --- Best Practices --- */
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/* line numbers (not yet implemented) */
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/* Internet related */
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/* for ChangeLog and Log files */
pre.sh_sourceCode .sh_date { color: blue; font-weight: bold; }
pre.sh_sourceCode .sh_time, pre.sh_sourceCode .sh_file { color: #00008B; font-weight: bold; }
pre.sh_sourceCode .sh_ip, pre.sh_sourceCode .sh_name { color: #006400; }

/* for Prolog, Perl... */
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pre.sh_sourceCode .sh_bibtex { color: blue; }

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pre.sh_sourceCode .sh_newfile { color: #006400; }
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pre.sh_sourceCode .sh_paren { color: red; }
pre.sh_sourceCode .sh_attribute { color: #006400; }

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<body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C" /></a></p><h1 class="title" id="title">Microdata to RDF</h1><h2 id="subtitle">Transformation from HTML+Microdata to RDF</h2><h2 id="w3c-working-draft-12-january-2012"><acronym title="World Wide Web Consortium">W3C</acronym> Working Draft 12 January 2012</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2012/WD-microdata-rdf-20120112/">http://www.w3.org/TR/2012/WD-microdata-rdf-20120112/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/microdata-rdf/">http://www.w3.org/TR/microdata-rdf/</a></dd><dt>Latest editor's draft:</dt><dd><a href="https://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/index.html">https://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/index.html</a></dd><dt>Editor:</dt><dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, Kellogg Associates</dd>
<dt>Authors:</dt><dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
<dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, Kellogg Associates</dd>
<dd><a href="http://www.jenitennison.com/">Jeni Tennison</a>, Independent</dd>
</dl>
<p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2012 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></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>

<hr /></div>
<div id="abstract" class="introductory section"><h2>Abstract</h2>
  <p>HTML microdata [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>] is an extension to HTML used to embed machine-readable data into HTML documents.
    Whereas the microdata specification describes a means of markup, the output format is JSON. This specification
    describes processing rules that may be used to extract RDF [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>] from an HTML document containing
    microdata.</p>
</div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><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 <acronym title="World Wide Web Consortium">W3C</acronym> publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><acronym title="World Wide Web Consortium">W3C</acronym> technical reports index</a> at http://www.w3.org/TR/.</em></p>
<p>This document is an experimental work in progress. The concepts described herein are intended to 
  provide guidance for a possible future Working Group chartered to provide a Recommendation
  for this transformation. As a consequence, implementers of this specification, either producers
  or consumers, should note that it may change prior to any possible publication as a Recommendation.</p>
<p>This document was published by the <a href="http://www.w3.org/2001/sw/interest/">HTML Data Task Force, Semantic Web Interest Group</a> as a First Public Working Draft. If you wish to make comments regarding this document, please send them to <a href="mailto:public-html-data-tf@w3.org">public-html-data-tf@w3.org</a> (<a href="mailto:public-html-data-tf-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-html-data-tf/">archives</a>). All feedback is welcome.</p>

<p>Publication as a Working Draft does not imply endorsement by the <acronym
          title="World Wide Web Consortium">W3C</acronym>
        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. The disclosure obligations
        of the Participants of this group are described in the <a href="http://www.w3.org/2003/12/swa/swig-charter">charter</a>.</p>


</div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a><ul class="toc"><li class="tocline"><a href="#background" class="tocxref"><span class="secno">1.1 </span>Background</a></li><li class="tocline"><a href="#use-cases" class="tocxref"><span class="secno">1.2 </span>Use Cases</a></li><li class="tocline"><a href="#issues" class="tocxref"><span class="secno">1.3 </span>Issues</a></li></ul></li><li class="tocline"><a href="#attributes-and-syntax" class="tocxref"><span class="secno">2. </span>Attributes and Syntax</a></li><li class="tocline"><a href="#vocabulary-registry" class="tocxref"><span class="secno">3. </span>Vocabulary Registry</a><ul class="toc"><li class="tocline"><a href="#property-uri-generation" class="tocxref"><span class="secno">3.1 </span>Property URI Generation</a></li><li class="tocline"><a href="#value-ordering" class="tocxref"><span class="secno">3.2 </span>Value Ordering</a></li><li class="tocline"><a href="#value-typing" class="tocxref"><span class="secno">3.3 </span>Value Typing</a></li></ul></li><li class="tocline"><a href="#algorithm" class="tocxref"><span class="secno">4. </span>Algorithm</a><ul class="toc"><li class="tocline"><a href="#algorithm-terms" class="tocxref"><span class="secno">4.1 </span>Algorithm Terms</a></li><li class="tocline"><a href="#rdf-conversion-algorithm" class="tocxref"><span class="secno">4.2 </span>RDF Conversion Algorithm</a></li><li class="tocline"><a href="#generate-the-triples" class="tocxref"><span class="secno">4.3 </span>Generate the triples</a></li><li class="tocline"><a href="#generate-predicate-uri" class="tocxref"><span class="secno">4.4 </span>Generate Predicate URI</a></li><li class="tocline"><a href="#generate-property-values" class="tocxref"><span class="secno">4.5 </span>Generate Property Values</a></li><li class="tocline"><a href="#generate-collection" class="tocxref"><span class="secno">4.6 </span>Generate RDF Collection</a></li></ul></li><li class="tocline"><a href="#markup-examples" class="tocxref"><span class="secno">A. </span>Markup Examples</a></li><li class="tocline"><a href="#example-registry" class="tocxref"><span class="secno">B. </span>Example <span class="tref internalDFN formerLink tref internalDFN" title="registry">registry</span></a><ul class="toc"><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">B.1 </span>Acknowledgements</a></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">C. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">C.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">C.2 </span>Informative references</a></li></ul></li></ul></div>



<div class="informative section" id="introduction">
  
<!-- OddPage -->
<h2><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
  <p>This document describes a means of transforming HTML containing microdata into RDF. HTML Microdata [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]
    is an extension to HTML used to embed machine-readable data to HTML documents. This specification describes
    transformation directly to RDF [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>].</p>
  <div class="note">
    <p>There are a variety of ways in which a mapping from microdata to
      RDF might be configured to give a result that is closer to the required result for a particular vocabulary. This
      specification defines terms that can be used as hooks for vocabulary-specific behavior, which could be defined
      within a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> or on an implementation-defined basis. However, the HTML Data TF recommends the
      adoption of a single method of mapping in which every vocabulary is treated as if:</p>
    <ul>
      <li><a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> is set to <code>vocabulary</code> </li>
      <li><a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> is set to <code>unordered</code></li>
    </ul>
    <p>For background on the trade-offs between these options, see 
      <a href="http://www.w3.org/wiki/Mapping_Microdata_to_RDF">http://www.w3.org/wiki/Mapping_Microdata_to_RDF</a>.</p>
  </div>
<div class="informative section" id="background">
  <h3><span class="secno">1.1 </span>Background</h3><p><em>This section is non-normative.</em></p>
  <p>Microdata [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>] is a way of embedding data in HTML documents
    using attributes. The HTML DOM is extended to provide an API for
    accessing microdata information, and the microdata specification
    defines how to generate a JSON representation from microdata markup.</p>

  <p>Mapping microdata to RDF enables consumers to merge data expressed
    in other RDF-based formats with microdata. It facilitates the use of
    RDF vocabularies within microdata, and enables microdata to be used
    with the full RDF toolchain. Some use cases for this mapping are
    described in <a href="#use-cases">Section 1.2</a> below.</p>

  <p>Microdata's data model does not align neatly with RDF.</p>
  <ul>
   <li>Non-URL microdata properties are disambiguated based on microdata
     <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>; an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> with the type <code>http://example.org/Cat</code> can have
     both the property <code>color</code> and the property <code>http://example.org/color</code>,
     and these properties are semantically distinct under microdata. In
     RDF, all properties have IRIs.</li>

   <li>When an item has multiple properties with the same name, the values are
     always ordered; in RDF, property values are unordered unless they
     are explicitly listed in an <a class="tref internalDFN" title="rdf_collection" href="#dfn-rdf_collection">RDF Collection</a>.</li>

   <li>A value in microdata is always a simple string which is interpreted
     by the consuming application. In RDF, values can be tagged with a
     datatype or a language. According to the microdata specification, the
     HTML context of microdata markup should not change how microdata is
     interpreted, so although element names and HTML <code>@lang</code> attributes could
     be used to provide datatype and language information for RDF data, this
     would be contrary to the microdata specification.</li>
  </ul>

   <p>Thus, in some places the needs of RDF consumers violate requirements of
     the microdata specification. This specification highlights where such
     violations occur and the reasons for them.</p>

   <p>This specification allows for 
     <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a>-specific rules that affect the generation of property URIs and value serializations.
     This is facilitated by a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> that associates URIs with specific rules based on matching
     <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a> values against registered URI prefixes do determine a vocabulary and potentially
     vocabulary-specific processing rules.</p>

   <p>This specification also assumes that consumers of RDF generated from
     microdata may have to process the results in order to, for example,
     assign appropriate datatypes to <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a>s.</p>
</div>

<div class="informative section" id="use-cases">
  <h3><span class="secno">1.2 </span>Use Cases</h3><p><em>This section is non-normative.</em></p>
  <p>During the period of the task force, a number of use cases were put forth for the use of microdata
    in generating RDF:</p>
  <ul>
    <li>Semantic search engines such as <a href="http://sindice.com/">Sindice</a> use RDF as their backend data model.
      They want to gather information expressed using microdata alongside information expressed in RDF-based formats
      and make it available to others to use, as a service. In these cases, the ultimate consumer, who will need to
      understand the vocabularies used within the microdata, is the program or person who pulls out data from Sindice.
      Sindice needs to retain the distinctions in the original microdata (e.g. ordering of items) and might not have
      built-in knowledge about the <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> of interest to the ultimate consumer. In this case, the ultimate consumer
      is likely to have to map/validate/handle errors in the data they get from Sindice.</li>
    <li>A consumer such as <a href="http://openelectiondata.org">openelectiondata.org</a> wants to support
      microdata-based markup of their <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> as well as RDFa-based markup, both going into an RDF-based data store.
      They want to use an off-the-shelf tool to extract the microdata. They want to configure the tool to give them the
      RDF that is appropriate for their known <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a>.</li>
    <li>A browser plugin that captures data for the user uses an RDF model as its backend store.
      Any time it encounters microdata on a page, it wants to pull that microdata into the store on the fly.</li>
    <li><a href="http://purl.org/goodrelations/">GoodRelations</a> properties do not take
      <a class="tref internalDFN" title="rdf_collection" href="#dfn-rdf_collection">rdf:List</a> values; when they take
      multiple values they are unordered. The <code>rdfs:range</code> of a GoodRelations
      property indicates the datatype of the expected value, and GoodRelations
      processors will expect values to be cast to that type. Language
      information from the HTML needs to be captured as it is common that
      multiple values will be used to specify the same information in different
      languages.</li>
    <li><a href="http://schema.org/">Schema.org</a> has an 
      <a href="http://schema.org/docs/extension.html">extension mechanism</a> to allow authors to express information
      that is more detail than the pre-defined types, properties and enumerations. Property URIs are all in the same
      flat-namespace as types, but authors can add more detail by using a '/' after the type or property to provide
      more detail. For example, schema.org defines a <em>musicGroupMember</em> property having a URI of
      <code>http://schema.org/musicGroupMember</code>, and an author might express more detail through an ad-hoc
      sub-property <em>musicGroupMember/leadVocalist</em>, having the URI
      <code>http://schema.org/musicGroupMember/leadVocalist</code>.</li>
  </ul>
</div>

<div class="informative section" id="issues">
  <h3><span class="secno">1.3 </span>Issues</h3><p><em>This section is non-normative.</em></p>
  <p>Decisions or open issues in the specification are tracked on the
    <a href="http://www.w3.org/2011/htmldata/track/issues">Task Force Issue Tracker</a>. These include the
    following:</p>
  <dl>
    <dt><a href="http://www.w3.org/2011/htmldata/track/issues/1">ISSUE 1</a></dt><dd>
      Vocabulary specific parsing for Microdata. This specification attempts to create generic
      rules for processing microdata with typical RDF vocabularies. A <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> allows
      for exceptions to the default processing rules for certain well-known vocabularies.
    </dd>
    <dt><a href="http://www.w3.org/2011/htmldata/track/issues/2">ISSUE 2</a></dt><dd>
      Should Microdata-RDF generate XMLLiteral values. This issue has been closed with no change
      as this would violate microdata's data model.
    </dd>
    <dt><a href="http://www.w3.org/2011/htmldata/track/issues/3">ISSUE 3</a></dt><dd>
      Should the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> allow property datatype specification. The consensus is that datatypes are only derived from HTML semantics, so that only &lt;time&gt; values have a datatype other than plain.
    </dd>
    <dt><a href="http://www.w3.org/2011/htmldata/track/issues/4">ISSUE 4</a></dt><dd>
      Should the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> allow a <a class="tref internalDFN" title="name" href="#dfn-name">name</a> or URL to be used as an alias for <a class="aref internalDFN" title="itemid" href="#dfn-itemid">@itemid</a>.
    </dd>
  </dl>

  <p>The purpose of this specification is to provide input to a future working group that can make decisions
    about the need for a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> and the details of processing. Among the options investigated by
    the Task Force are the following:</p>
  <ul>
    <li>Property URI generation using the original microdata specification with a base URI and
      <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.5">fragment</a></cite> made up of the in-scope <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item
      type</a> and <a class="tref internalDFN" title="properties" href="#dfn-properties">properties</a>.</li>
    <li>Vocabulary-based URI generation, where the <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> is determined from the
      in-scope <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>, either through an algorithmic modification of the type URL or by matching the
      URL against a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a>. The vocabulary URI is then used to generate property URIs in a namespace
      parallel to the type URI.</li>
    <li>When there are multiple <a class="tref internalDFN" title="top-level_item" href="#dfn-top-level_item">top-level item</a>s in a document, place items in an RDF Collection.
      Alternatively, simply list the items as multiple values, or do not generate an
      <code>http://www.w3.org/ns/md#item</code> mapping at all.</li>
    <li>When an item has multiple values for a given <a class="tref internalDFN" title="property" href="#dfn-property">property</a>, place the values in an RDF Collection.
      Alternatively, do not use collections, use an alternative such as <code>rdf:Seq</code>, or place all values,
      whether or not multiple, into some form of collection.</li>
  </ul>
</div>
</div>

<div id="attributes-and-syntax" class="section">
  
<!-- OddPage -->
<h2><span class="secno">2. </span>Attributes and Syntax</h2>
  <p>
    The microdata specification [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>] defines a number of attributes and the way in which those
    attributes are to be interpreted. The
    <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">microdata DOM API</a></cite>
    provides methods and attributes for retrieving microdata from the HTML DOM.
  </p><p>For reference, attributes used for specifying and retrieving HTML microdata are referenced here:</p>
  <dl>
    <dt><dfn class="adef" title="itemid" id="dfn-itemid">itemid</dfn></dt><dd>
      An attribute containing a URL used to identify the subject of triples associated with this <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
      (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemid">Items</a></cite>
      in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
    </dd>
    <dt><dfn class="adef" title="itemprop" id="dfn-itemprop">itemprop</dfn></dt><dd>
      An attribute used to identify one or more <a class="tref internalDFN" title="name" href="#dfn-name">name</a>s of an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>s. An <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a>
      contains a space separated list of <dfn title="name" id="dfn-name">name</dfn>s which may either by <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>s or terms
      associated with the type of the <a class="tref internalDFN" title="item" href="#dfn-item">item</a> as defined by the referencing <a class="tref internalDFN" title="item" href="#dfn-item">item</a>'s
      <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>.
      (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#names:-the-itemprop-attribute">Items</a></cite>
      in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
    </dd>
    <dt><dfn class="adef" title="itemref" id="dfn-itemref">itemref</dfn></dt><dd>
      An additional attribute on an element that references additional elements containing property
      definitions to be applied to the referencing <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
      (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemref">Items</a></cite>
      in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
    </dd>
    <dt><dfn class="adef" title="itemscope" id="dfn-itemscope">itemscope</dfn></dt><dd>
      An boolean attribute identifying an element as an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
      (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemscope">Items</a></cite>
      in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
    </dd>
    <dt><dfn class="adef" title="itemtype" id="dfn-itemtype">itemtype</dfn></dt><dd>
      An additional attribute on an element used to specify one or more types of an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
      The <dfn title="item_type" id="dfn-item_type">item type</dfn> of an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> is the first value returned from
      <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
      on the element.
      The <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a> is also used to resolve non-URL <a class="tref internalDFN" title="name" href="#dfn-name">name</a>s to <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>s.
      Available through the
      <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite> as
      <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>.
      (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemtype">Items</a></cite>
      in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
    </dd>
  </dl>
  <p>In RDF, it is common for people to shorten vocabulary terms via abbreviated URIs that use a 'prefix'
    and a 'reference'. throughout this document assume that the following vocabulary
    prefixes have been defined:</p>
  <table><tbody>
    <tr>
      <td>dc:</td>
      <td>http://purl.org/dc/terms/</td>
    </tr>

    <tr>
      <td>md:</td>
      <td>
        http://www.w3.org/ns/md#</td>
    </tr>

    <tr>
      <td>rdf:</td>
      <td>
        http://www.w3.org/1999/02/22-rdf-syntax-ns#</td>
    </tr>

    <tr>
      <td>rdfs:</td>
      <td>
        http://www.w3.org/2000/01/rdf-schema#</td>
    </tr>

    <tr>
      <td>xsd:</td>
      <td>http://www.w3.org/2001/XMLSchema#</td>
    </tr>
  </tbody></table>
</div>

<div class="informative section" id="vocabulary-registry">
  
<!-- OddPage -->
<h2><span class="secno">3. </span>Vocabulary Registry</h2><p><em>This section is non-normative.</em></p>
  <p>In a perfect world, all processors would be able to generate the same output for a given input
    without regards to the requirements of a particular <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a>. However, microdata doesn't
    provide sufficient syntactic help in making these decisions. Different vocabularies have different
    needs.</p>
  <p>The registry is located at the namespace defined for microdata: <code>http://www.w3.org/ns/md</code> in
    a variety of formats.</p>
  <p>The <dfn title="registry" id="dfn-registry">registry</dfn> associates a <dfn title="uri_prefix" id="dfn-uri_prefix">URI prefix</dfn> with one or more key-value pairs denoting
  processor behavior. A hypothetical JSON representation of such a registry might be the following:</p>
<pre class="example">{
  &quot;http://schema.org/&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    &quot;multipleValues&quot;: &quot;unordered&quot;,
    &quot;properties&quot;: {
      &quot;tracks&quot;: {&quot;multipleValues&quot;: &quot;list&quot;}
    }
  },
  &quot;http://microformats.org/profile/hcard&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    &quot;multipleValues&quot;: &quot;list&quot;,
    &quot;properties&quot; {
      &quot;url&quot;: {&quot;multipleValues&quot;: &quot;unordered&quot;}
    }
  }
}</pre>
  <p>This structure associates mappings for two URIs, <code>http://schema.org/</code> and
    <code>http://microformats.org/profile/hcard</code>. Items having an <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a> with a <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI
    prefix</a> from this <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> use the the rules described for that prefix within the scope of that
    <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>. This mapping currently defines two rules: <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> and
    <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> with values to indicate specific behavior. It also allows overrides
    on a per-property basis; the <a class="tref internalDFN" title="properties" href="#dfn-properties"><code>properties</code></a> key associates an individual <a class="tref internalDFN" title="name" href="#dfn-name">name</a>
    with overrides for default behavior.
    The interpretation of these
    rules is defined in the following sections. If an item has no <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> or the
    <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains no <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> matching <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a>, a conforming
    processor <em class="rfc2119" title="must">must</em> use the default values defined for these rules.</p>
  <p class="note">The concept of a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a>, including a hypothetical format, location and updating rules
    is presented as an abstract concept useful for describing the function of a microdata processor.
    There are issues surrounding update
    frequency, URL naming, and how updates are authorized. This spec
    just considers the semantic content of such a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> and how it can be used to affect processing without
    defining its representation or update policies.</p>
  <p class="issue">Richard Ciganiak has
    <cite><a href="http://richard.cyganiak.de/2011/10/microdata.html#whitelists">pointed out</a></cite> that
    &quot;Registry&quot; may be the wrong term, as the proposed <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> doesn't assign identifiers or manage
    namespace, it simply provides a mapping between <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>ss and processor behavior and suggests the term
    &quot;Whitelist&quot;. As more than two values are required, and it describes more than binary behavior, this term
    isn't appropriate either.</p>

<div class="informative section" id="property-uri-generation">
  <h3><span class="secno">3.1 </span>Property URI Generation</h3><p><em>This section is non-normative.</em></p>
  <p>For <a class="tref internalDFN" title="name" href="#dfn-name">name</a>s which are not <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>s,
    the <dfn title="propertyuri" id="dfn-propertyuri"><code>propertyURI</code></dfn> rule defines the algorithm for generating an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>
    given an <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">evaluation context</a> including a <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a>, <a class="tref internalDFN" title="current_name" href="#dfn-current_name">current name</a> and
    <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a>.</p>
  <p>The procedure for generating property URIs is defined in
    <a href="#generate-predicate-uri">Generate Predicate URI</a>.</p>
  <p>Possible values for <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> are the following:</p>
  <dl>
    <dt><code>contextual</code></dt><dd>
      The <code>contextual</code> URI generation scheme guarantees that generated property URIs are
      unique based on the value of <a class="tref internalDFN" title="current_name" href="#dfn-current_name">current name</a>. This is
      required as the microdata data model requires that <a class="tref internalDFN" title="name" href="#dfn-name">name</a>s are associated with specific
      items and do not have a global scope. (See <a href="#scheme-context">Step 5</a> in
      <a href="#generate-predicate-uri">Generate Predicate URI</a>).
      <div>
        <p>URI creation uses a base URI with query parameters to indicate the in-scope
          type and <a class="tref internalDFN" title="name" href="#dfn-name">name</a> list. Consider the following example:</p>
        <pre class="example">&lt;span itemscope itemtype=&quot;http://microformats.org/profile/hcard&quot;&gt;
  &lt;span itemprop=&quot;n&quot; itemscope&gt;
    &lt;span itemprop=&quot;given-name&quot;&gt;
      Princeton
    &lt;/span&gt;
  &lt;/span&gt;
&lt;/span&gt;</pre>
        <p>The first <a class="tref internalDFN" title="name" href="#dfn-name">name</a> <em>n</em> generates the URI
          <code>http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop=n</code>.
          However, the included <a class="tref internalDFN" title="name" href="#dfn-name">name</a> <em>given-name</em> is included in untyped item.
          The inherited property URI is used to create a new property URI:
          <code>http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop=n.given-name</code>.</p>
        <p>This scheme is compatible with the needs of other RDF serialization formats such as
          RDF/XML [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>],
          which rely on <em>QNames</em> for expressing properties. For example, the generated property URIs
          can be split as follows:
        </p><pre class="example">&lt;rdf:Description xmlns:hcard=&quot;http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop=&quot;
                 rdf:type=&quot;http://microformats.org/profile/hcard&quot;&gt;
  &lt;hcard:n&gt;
    &lt;rdf:Description&gt;
      &lt;hcard:n.given-name&gt;
        Princeton
      &lt;/hcard:n.given-name&gt;
    &lt;/rdf:Description&gt;
  &lt;/hcard:n&gt;
&lt;/rdf:Description&gt;</pre>
        <p>Looking at another example:</p>
        <pre class="example">&lt;div itemscope itemtype=&quot;http://schema.org/Person&quot;&gt;
  &lt;h2 itemprop=&quot;name&quot;&gt;Jeni&lt;/h2&gt;
&lt;/div&gt;</pre>
        <p>This would generate <code>http://www.w3.org/ns/md?type=http://schema.org/Person&amp;prop=name</code>.</p>
      </div>
    </dd>
    <dt><code>vocabulary</code></dt><dd>
      The <code>vocabulary</code> URI generation scheme appends <a class="tref internalDFN" title="name" href="#dfn-name">name</a>s that are not
      <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>s to the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>. When generating property URIs, if the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>
      does not end with a '/' or '#', a '#' is appended to the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>. (See <a href="#scheme-vocab">Step 4</a>
      in
      <a href="#generate-predicate-uri">Generate Predicate URI</a>.)
      <div>
        <p>URI creation uses a base URL with query parameters to indicate the in-scope
          type and <a class="tref internalDFN" title="name" href="#dfn-name">name</a> list. Consider the following example:</p>
        <pre class="example">&lt;span itemscope itemtype=&quot;http://microformats.org/profile/hcard&quot;&gt;
  &lt;span itemprop=&quot;n&quot; itemscope&gt;
    &lt;span itemprop=&quot;given-name&quot;&gt;
      Princeton
    &lt;/span&gt;
  &lt;/span&gt;
&lt;/span&gt;</pre>
        <p>Given the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> <code>http://microformats.org/profile/hcard</code>, this
          would generate <code>http://microformats.org/profile/hcard#n</code> and
          <code>http://microformats.org/profile/hcard#given-name</code>. Note that the '#' is automatically
          added as a separator.
        </p><p>Looking at another example:</p>
        <pre class="example">&lt;div itemscope itemtype=&quot;http://schema.org/Person&quot;&gt;
  &lt;h2 itemprop=&quot;name&quot;&gt;Jeni&lt;/h2&gt;
&lt;/div&gt;</pre>
        <p>Given the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> <code>http://schema.org/</code>,
          this would generate <code>http://schema.org/name</code>. Note that if the <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a>
          were <code>http://schema.org/Person/Teacher</code>, this would generate the same property URI.</p>
      </div>
    </dd>
  </dl>
  <p>If the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains no match for <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> implementations act as if
    there is a <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> made from the first <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a> value by stripping either the <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.5">fragment</a></cite> content or <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.3">last path segment</a></cite>, if the value has no fragment (See
    [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC3986">RFC3986</a></cite>]).</p>
  <p class="note">Deconstructing the <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a> URL to create or identify a vocabulary URI
    is a violation of the microdata specification which is necessary to
    support the use of existing vocabularies designed for use with RDF, and
    shared or inherited properties within all vocabularies.</p>
  <p>The default value of <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> is <code>vocabulary</code>.</p>
  <pre class="example">&lt;div itemscope itemtype=&quot;http://schema.org/Book&quot;&gt;
  &lt;h2 itemprop=&quot;title&quot;&gt;Just a Geek&lt;/h2&gt;
&lt;/div&gt;</pre>
  <p>In this example, assuming no matching entry in the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a>,
    the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> is constructed by removing the
    <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.3">last path segment</a></cite>, leaving the URI
    <code>http://schema.org/</code>. As there is no explicit <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a>,
    the default <code>vocabulary</code> is used, and the resulting property URI would be
    <code>http://schema.org/title</code>.</p>
</div>

<div class="informative section" id="value-ordering">
  <h3><span class="secno">3.2 </span>Value Ordering</h3><p><em>This section is non-normative.</em></p>
  <p>For items having multiple values for a given <a class="tref internalDFN" title="property" href="#dfn-property">property</a>,
    the <dfn title="multiplevalues" id="dfn-multiplevalues"><code>multipleValues</code></dfn> rule defines the algorithm for serializing these values.
    Microdata uses document order when generating <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a>s, as defined in
    <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite>
    as <code>element.itemValue</code>. However, many RDF vocabularies expect multiple values to be generated
    as triples sharing a common subject and predicate. In some cases, it may be useful to retain value ordering.</p>
  <p>The procedure for generating <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a>s is defined in
    <a href="#generate-property-values">Generate Property Values</a>.</p>
  <p>Possible values for <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> are the following:</p>
  <dl>
    <dt><code>unordered</code></dt><dd>
      Values are serialized without ordering using a common subject and predicate.
      (See <a href="#values-unordered">Step 7</a> in
      <a href="#generate-property-values">Generate Property Values</a>).
    </dd>
    <dt><code>list</code></dt><dd>
      Multi-valued <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a>s are serialized using an <a class="tref internalDFN" title="rdf_collection" href="#dfn-rdf_collection">RDF Collection</a>.
      (See <a href="#values-list">Step 8</a> in
      <a href="#generate-property-values">Generate Property Values</a>).
    </dd>
  </dl>
  <p>An example of how this might be specified in a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> is the following:</p>
  <pre class="example">{
  &quot;http://schema.org/&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    <span class="diff">&quot;multipleValues&quot;: &quot;unordered&quot;</span>
  },
  &quot;http://microformats.org/profile/hcard&quot;: {
    &quot;propertyURI&quot;:    &quot;type&quot;,
    <span class="diff">&quot;multipleValues&quot;: {&quot;multipleValues&quot;: &quot;list&quot;}</span>
  }
}</pre>
  <p>Additionally, some vocabularies may wish to specify this on a per-property basis. For example,
    within <code>http://schema.org/MusicPlaylist</code> the <code>tracks</code> property might depend on the order
    of values to to reproduce associated <code>MusicRecording</code> values.</p>
  <pre class="example">{
 &quot;http://schema.org/&quot;: {
   &quot;propertyURI&quot;: &quot;vocabulary&quot;,
   &quot;multipleValues&quot;: &quot;unordered&quot;<span class="diff">,
   &quot;properties&quot;: {
     &quot;tracks&quot;: {&quot;multipleValues&quot;: &quot;list&quot;}
   }</span>
 }
}</pre>
  <p>The <dfn title="properties" id="dfn-properties"><code>properties</code></dfn> key takes a JSON Object as a value, which in turn has keys for each
    property that is to be given alternate semantics. Each <a class="tref internalDFN" title="name" href="#dfn-name">name</a> is implicitly expanded to it's URI
    representation as defined in <a href="#generate-predicate-uri">Generate Predicate URI</a>, so that
    the behavior is the same whether or not the <a class="tref internalDFN" title="name" href="#dfn-name">name</a> is listed as an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>.</p>
  <p>The default value of <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> is <code>unordered</code>.</p>
  <div class="note">
    <p>An alternative mechanism would output <em>both</em> unordered and ordered values, to allow an application
    to choose the most useful representation. For example, consider the following:</p>
<pre class="example">&lt;div itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicPlaylist&quot;&gt;
  &lt;span itemprop=&quot;name&quot;&gt;Classic Rock Playlist&lt;/span&gt;
  &lt;meta itemprop=&quot;numTracks&quot; content=&quot;2&quot;/&gt;
  &lt;p&gt;Including works by
    &lt;span itemprop=&quot;byArtist&quot;&gt;Lynard Skynard&lt;/span&gt; and
    &lt;span itemprop=&quot;byArtist&quot;&gt;AC/DC&lt;/span&gt;&lt;/p&gt;.

  &lt;div itemprop=&quot;tracks&quot; itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicRecording&quot;&gt;
    1.&lt;span itemprop=&quot;name&quot;&gt;Sweet Home Alabama&lt;/span&gt; -
    &lt;span itemprop=&quot;byArtist&quot;&gt;Lynard Skynard&lt;/span&gt;
    &lt;link href=&quot;sweet-home-alabama&quot; itemprop=&quot;url&quot; /&gt;
   &lt;/div&gt;

  &lt;div itemprop=&quot;tracks&quot; itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicRecording&quot;&gt;
    2.&lt;span itemprop=&quot;name&quot;&gt;Shook you all Night Long&lt;/span&gt; -
    &lt;span itemprop=&quot;byArtist&quot;&gt;AC/DC&lt;/span&gt;
    &lt;link href=&quot;shook-you-all-night-long&quot; itemprop=&quot;url&quot; /&gt;
  &lt;/div&gt;
&lt;/div&gt;</pre>
    <p>This might generate the following Turtle:</p>
<pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
@prefix schema: &lt;http://schema.org/&gt; .

&lt;&gt; md:item [ a schema:MusicPlaylist;
  schema:name &quot;Classic Rock Playlist&quot;;
  schema:byArtist (&quot;Lynard Skynard&quot; &quot;AC/DC&quot;);
  schema:numTracks &quot;2&quot;;
  schema:tracks _:track1, _:track2, (_:track1 _:track2)
] .
_:track1 a schema:MusicRecording;
  schema:byArtist (&quot;Lynard Skynard&quot;);
  schema:name &quot;Sweet Home Alabama&quot;;
  schema:url &lt;sweet-home-alabama&gt; .
_:track2 a schema:MusicRecording;
  schema:byArtist (&quot;AC/DC&quot;);
  schema:name &quot;Shook you all Night Long&quot;;
  schema:url &lt;shook-you-all-night-long&gt; .</pre>
    <p>By providing both <code>_:track1</code> and <code>_:track2</code> as object values of the playlist
      along with an RDF Collection containing the ordered values, the data may be queried via a simple
      query using the playlist subject, or as an ordered collection.</p>
  </div>
</div>

<div class="informative section" id="value-typing">
  <h3><span class="secno">3.3 </span>Value Typing</h3><p><em>This section is non-normative.</em></p>
  <p>In microdata, all values are strings. In RDF, values may be resources
   or may be typed with an appropriate datatype.</p>
  <p> In some cases, the type of a microdata value can be determined from the
   element on which it is specified. In particular:</p>
  <ul>
    <li>URL property elements provide URLs</li>
    <li><code>time</code> element provides dates and times</li>
  </ul>
  <p class="issue">Using information about the content of the document where the microdata
   is marked up <em>might</em> be a violation of the spirit of the microdata specification, though it does not explicitly say in
   normative text that consumers cannot use other information from the HTML DOM to interpret microdata.</p>

  <p>Additionally, one possible use of a <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> would allow vocabularies to be marked with datatype information,
    so that a <code>dc:time</code> value, for example, would be understood to represent a literal with datatype
    <code>xsd:date</code>. This could be done by adding information for each property in the vocabulary requiring
    special treatment.</p>
  <p>This might be represented using a syntax such as the following:</p>
  <pre class="example">{
 &quot;http://schema.org/&quot;: {
   &quot;propertyURI&quot;: &quot;vocabulary&quot;,
   &quot;multipleValues&quot;: &quot;unordered&quot;<span class="diff">,
   &quot;properties&quot;: {
     &quot;dateCreated&quot;: {&quot;datatype&quot;: &quot;http://www.w3.org/2001/XMLSchema#date&quot;}
   }</span>
 }
}</pre>
  <p>The <code>datatype</code> identifies a URI to be used in constructing a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a>.</p>

  <p>In most cases, the relevant datatype for a value can be derived from
    knowledge of what property the value is for and the syntax of the value
    itself. Thus, values can be given datatypes in a post-processing step
    after the mapping of microdata to RDF described by this specification.
    However, where there is information in the HTML markup, such as knowledge
    of what element was used to mark up the value, which can help with
    determining its datatype, that information is used by this specification.</p>
  <p>This concept is not explored further at this time, but could be developed further in
    a future revision of this document.</p>
</div>

<p class="note">If property URI generation was fixed to <code>vocabulary</code>, multiple values always
  generated both <code>unordered</code> and <code>ordered</code> representations, and there were <code>datatype</code>
  support, the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> could be reduced to a simple list of URLs without any further structure necessary.</p>
</div>

<div id="algorithm" class="section">
  
<!-- OddPage -->
<h2><span class="secno">4. </span>Algorithm</h2>
  <p>
    Transformation of Microdata to RDF makes use of general processing rules described in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]
    for the treatment of <a class="tref internalDFN" title="item" href="#dfn-item">item</a>s.
  </p>
  <div id="algorithm-terms" class="section">
    <h3><span class="secno">4.1 </span>Algorithm Terms</h3>
    <dl>
      <dt><dfn title="absolute_url" id="dfn-absolute_url">absolute URL</dfn></dt><dd>
        The term <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/urls.html#absolute-url">absolute URL</a></cite>
        is defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>].
      </dd>
      <dt><dfn title="blank_node" id="dfn-blank_node">blank node</dfn></dt><dd>
        A blank node is a node in a graph that is neither a <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> nor a <a class="tref internalDFN" title="literal" href="#dfn-literal">literal</a>.
        <a class="tref internalDFN" title="item" href="#dfn-item">Item</a>s without a <a class="tref internalDFN" title="global_identifier" href="#dfn-global_identifier">global identifier</a> have a blank node allocated to them.
        (See [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
      </dd>
      <dt><dfn title="document_base" id="dfn-document_base">document base</dfn></dt><dd>
        The base address of the document being processed, as defined in <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/urls.html#resolving-urls">Resolving URLs</a></cite> in
        [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>].
      </dd>
      <dt><dfn title="evaluation_context" id="dfn-evaluation_context">evaluation context</dfn></dt><dd>
        A data structure including the following elements:
        <dl>
          <dt><dfn title="memory" id="dfn-memory">memory</dfn></dt><dd>
            a mapping of items to subjects, initially empty;
          </dd>
          <dt><dfn title="current_name" id="dfn-current_name">current name</dfn></dt><dd>
            an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a> for the in-scope <a class="tref internalDFN" title="name" href="#dfn-name">name</a>, used for generating URIs
            for properties of items without an <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>;
            <div class="note">
              <a class="tref internalDFN" title="current_name" href="#dfn-current_name">current name</a> is required for the <code>contextual</code> property URI generation
              scheme. Without this scheme, this evaluation context component would not be required.
            </div>
          </dd>
          <dt><dfn title="current_type" id="dfn-current_type">current type</dfn></dt><dd>
            an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a> for the <em>current type</em>, used when an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> does not
            contain an <a class="tref internalDFN" title="item_type" href="#dfn-item_type">item type</a>;
          </dd>
          <dt><dfn title="current_vocabulary" id="dfn-current_vocabulary">current vocabulary</dfn></dt><dd>
            an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a> for the <em>current vocabulary</em>, from the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a>.
          </dd>
        </dl>
      </dd>
      <dt><dfn title="item" id="dfn-item">item</dfn></dt><dd>
         An <a class="tref internalDFN" title="item" href="#dfn-item">item</a> is described by an element containing an <a class="aref internalDFN" title="itemscope" href="#dfn-itemscope">@itemscope</a> attribute. The list
         of top-level microdata items may be retrieved using the
         <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a>
         <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-document-getitems">document.getItems</a></cite></code>
         method.
      </dd>
      <dt><dfn title="item_properties" id="dfn-item_properties">item properties</dfn></dt><dd>
        The mechanism for finding the <a class="tref internalDFN" title="item_properties" href="#dfn-item_properties">properties of an item</a> The list
         of item properties items may be retrieved using the
         <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a>
         <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-properties">element.properties</a></cite></code>
         attribute.
      </dd>
      <dt><dfn title="fragment-escape" id="dfn-fragment-escape">fragment-escape</dfn></dt><dd>
        The term <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/urls.html#fragment-escaped">fragment-escape</a></cite>
        is defined in [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>]. This involves transforming elements added to URLs to ensure that the result
        remains a valid URL. The following characters are subject to percent escaping:
        <ul>
          <li>U+0022 QUOTATION MARK character (&quot;)</li>
          <li>U+0023 NUMBER SIGN character (#)</li>
          <li>U+0025 PERCENT SIGN character (%)</li>
          <li>U+003C LESS-THAN SIGN character (&lt;)</li>
          <li>U+003E GREATER-THAN SIGN character (&gt;)</li>
          <li>U+005B LEFT SQUARE BRACKET character ([)</li>
          <li>U+005C REVERSE SOLIDUS character (\)</li>
          <li>U+005D RIGHT SQUARE BRACKET character (])</li>
          <li>U+005E CIRCUMFLEX ACCENT character (^)</li>
          <li>U+007B LEFT CURLY BRACKET character ({)</li>
          <li>U+007C VERTICAL LINE character (|)</li>
          <li>U+007D RIGHT CURLY BRACKET character (})</li>
        </ul>
      </dd>
      <dt><dfn title="global_identifier" id="dfn-global_identifier">global identifier</dfn></dt><dd>
        The value of an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>'s <a class="aref internalDFN" title="itemid" href="#dfn-itemid">@itemid</a> attribute, if it has one. (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemscope">Items</a></cite> in
        [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
      </dd>
      <dt><dfn title="literal" id="dfn-literal">literal</dfn></dt><dd>
        Literals are values such as strings and dates, including <dfn title="typed_literal" id="dfn-typed_literal">typed literal</dfn>s and
        <dfn title="plain_literal" id="dfn-plain_literal">plain literal</dfn>s.
        (See [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
      </dd>
      <dt><dfn title="property" id="dfn-property">property</dfn></dt><dd>
        Each <a class="tref internalDFN" title="name" href="#dfn-name">name</a> identifies a <a class="tref internalDFN" title="property" href="#dfn-property">property</a> of an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
        An <a class="tref internalDFN" title="item" href="#dfn-item">item</a> may have multiple elements sharing the same <a class="tref internalDFN" title="name" href="#dfn-name">name</a>, creating
        a multi-valued <a class="tref internalDFN" title="property" href="#dfn-property">property</a>.
       </dd>
     <dt><dfn title="property_names" id="dfn-property_names">property names</dfn></dt><dd>
        The tokens of an element's <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a> attribute. Each token is a <a class="tref internalDFN" title="name" href="#dfn-name">name</a>.
        (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#property-names">Names: the
        itemprop attribute</a></cite> in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
      </dd>
      <dt><dfn title="property_value" id="dfn-property_value">property value</dfn></dt><dd>
        The <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a> of a name-value pair added by an element with an <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a>
        attribute depends on the element.
        <dl>
          <dt>If the element has no <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a> attribute</dt>
          <dd>The value is null and no triple should be generated.</dd>
          <dt>If the element creates an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> (by having an <a class="aref internalDFN" title="itemscope" href="#dfn-itemscope">@itemscope</a> attribute)</dt>
          <dd>
            The value is the <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a> returned from
            <a href="#generate-the-triples">generate the triples</a> for that <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
          </dd>
          <dt>If the element is a URL property element (<code>a</code>, <code>area</code>, <code>audio</code>,
            <code>embed</code>, <code>iframe</code>, <code>img</code>, <code>link</code>, <code>object</code>,
            <code>source</code>, <code>track</code> or <code>video</code>)</dt>
          <dd>
            The value is a <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> created from <code><cite>
              <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemvalue">element.itemValue</a></cite></code>.
              (See relevant attribute descriptions in [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>]).
          </dd>
          <dt>If the element is a <code>time</code> element.</dt>
          <dd>The value is a <a class="tref internalDFN" title="literal" href="#dfn-literal">literal</a> made from <code><cite>
            <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemvalue">element.itemValue</a></cite></code>.
          </dd><dd>
            <dl>
              <dt>
                If the value is a
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-date-string">
                  valid date string
                </a></cite>
                having the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#date">xsd:date</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
                <code>http://www.w3.org/2001/XMLSchema#date</code>.
              </dd>
              <dt>
                If the value is a
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-time-string">
                  valid time string
                </a></cite>
                having the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#time">xsd:time</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
                <code>http://www.w3.org/2001/XMLSchema#time</code>.
              </dd>
              <dt>
                If the value is a
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-local-date-and-time-string">
                  valid local date and time string
                </a></cite>
                or
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-global-date-and-time-string">
                  valid global date and time string
                </a></cite>
                having the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#dateTime">xsd:dateTime</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
               <code>http://www.w3.org/2001/XMLSchema#dateTime</code>.
              </dd>
              <dt>
                If the value is a
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-month-string">
                  valid month string
                </a></cite>
                having the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#gYearMonth">xsd:gYearMonth</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
               <code>http://www.w3.org/2001/XMLSchema#gYearMonth</code>.
              </dd>
              <dt>
                If the value is a
                <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-non-negative-integer">
                  valid non-negative integer
                </a></cite>
                having the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#gYearMonth">xsd:gYear</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
               <code>http://www.w3.org/2001/XMLSchema#gYearMonth</code>.
              </dd>
              <dt>
                If the value has the lexical form of
                <cite><a href="http://www.w3.org/TR/xmlschema-2/#duration">xsd:duration</a></cite> [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
              </dt>
              <dd>
                The value is a <a class="tref internalDFN" title="typed_literal" href="#dfn-typed_literal">typed literal</a> composed of the value and
                <code>http://www.w3.org/2001/XMLSchema#duration</code>.
                <p class="note">The referenced version of [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>] does not include a <em>duration</em> data type,
                  but it is in the Editor's Draft and is expected to be included in a
                  forthcoming update to the Working Draft</p>
              </dd>
              <dt>Otherwise</dt>
              <dd>
                The value is a <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a> created from the value with language information set from the <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/elements.html#the-lang-and-xml:lang-attributes">lang</a></cite> IDL attribute
                of the property element.
                <p class="note">The HTML
                  <em>valid yearless date string</em>
                  is similar to
                  <cite><a href="http://www.w3.org/TR/xmlschema-2/#gMonthDay">xsd:gMonthDay</a></cite>,
                  but the lexical forms differ, so it is not included in this conversion.</p>
              </dd>
            </dl>
            <p>See
              <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/rendering.html#the-time-element-0">
                The <code>time</code> element
              </a></cite>
              in [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>].</p>
          </dd>
          <dt>Otherwise</dt>
          <dd>The value is a <a class="tref internalDFN" title="plain_literal" href="#dfn-plain_literal">plain literal</a> created from <code><cite>
            <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemvalue">element.itemValue</a></cite></code>
            with language information set from the
            <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/elements.html#the-lang-and-xml:lang-attributes">lang</a></cite>
            IDL attribute of the property element.
          </dd>
        </dl>
      </dd>
      <dt><dfn title="top-level_item" id="dfn-top-level_item">top-level item</dfn></dt><dd>
        An <a class="tref internalDFN" title="item" href="#dfn-item">item</a> which does not contain an <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a> attribute.
        Available through the <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite> as
        <code>document.getItems</code>.
        (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#top-level-microdata-items">Associating names with items</a></cite> in [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>]).
      </dd>
      <dt><dfn title="uri_reference" id="dfn-uri_reference">URI reference</dfn></dt><dd>
        URI references are suitable to be used in <em>subject</em>, <em>predicate</em> or <em>object</em> positions
        within an RDF triple, as opposed to a <a class="tref internalDFN" title="literal" href="#dfn-literal">literal</a> value that may contain a string representation of a
        URI. (See [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
        <div class="issue">
          <p>The HTML5/microdata content model for <code>@href</code>, <code>@src</code>,
            <code>@data</code>, <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a> and <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a> and <a class="aref internalDFN" title="itemid" href="#dfn-itemid">@itemid</a> is that of
            a URL, not a URI or IRI.</p>
          <p>A proposed mechanism for specifying the range of <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a>s to be URI reference or IRI could
            allow these to be specified as subject or object using a <code>@content</code> attribute.
        </p></div>
      </dd>
      <dt><dfn title="vocabulary" id="dfn-vocabulary">vocabulary</dfn></dt><dd>
        A vocabulary is a collection of URIs, suitable for use as an <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a> or <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a>
        value, that share a common <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>. That prefix is the vocabulary URI. A vocabulary URI is not
        allowed to be a prefix of another vocabulary URI.
        <div class="note">
          This definition differs from the language in the HTML spec and is just for the purpose of this
          document. In HTML, a vocabulary is a specification, and doesn't have a URI. In our view, if one
          specification defines ten <a class="aref internalDFN" title="itemtype" href="#dfn-itemtype">@itemtype</a>s, then these could be treated as one vocabulary or as ten
          distinct vocabularies; it is entirely up to the vocabulary creator.
        </div>
      </dd>
    </dl>
  </div>

  <div id="rdf-conversion-algorithm" class="section">
    <h3><span class="secno">4.2 </span>RDF Conversion Algorithm</h3>
    <p>A HTML document containing microdata <em class="rfc2119" title="may">may</em> be converted to any other RDF-compatible document
    format using the algorithm specified in this section.</p>
    <p>A conforming microdata processor implementing RDF conversion <em class="rfc2119" title="must">must</em> implement a
      processing algorithm that results in the equivalent triples to those that the following
      algorithm generates:</p>

    <p>Set <em>item list</em> to an empty list.</p>

    <ol class="algorithm">
      <li>For each element that is also a <a class="tref internalDFN" title="top-level_item" href="#dfn-top-level_item">top-level item</a> run the following algorithm:
        <ol class="algorithm">
          <li>
            <a href="#generate-the-triples">Generate the triples</a> for an item <em>item</em>, using the
            <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">evaluation context</a>.
            Let <em>result</em> be the (<a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>) subject returned.
          </li>
          <li>
            Append <em>result</em> to <em>item list</em>.
          </li>
        </ol>
      </li>
      <li>
        <a href="#generate-collection">Generate an RDF Collection</a> <em>list</em> from the ordered list of values.
        Set <em>value</em> to the value returned from <a href="#generate-collection">generate an RDF
        Collection</a>.
      </li>
      <li>
        Generate the following triple:
        <dl class="triple">
          <dt>subject</dt>
          <dd><a class="tref internalDFN" title="document_base" href="#dfn-document_base">Document base</a></dd>
          <dt>predicate</dt>
          <dd><code>http://www.w3.org/ns/md#item</code></dd>
          <dt>object</dt>
          <dd><em>value</em></dd>
        </dl>
      </li>
    </ol>
  </div>

  <div id="generate-the-triples" class="section">
    <h3><span class="secno">4.3 </span>Generate the triples</h3>
    <p>
      When the user agent is to Generate triples for an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> <em>item</em>, given an
      <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">Evaluation Context</a>, it must run the following steps:
    </p>
    <p class="note">
      This algorithm has undergone substantial change from the original microdata specification [<cite><a class="bibref" rel="biblioentry" href="#bib-MICRODATA">MICRODATA</a></cite>].
    </p>
    <ol class="algorithm">
      <li>
        If there is an entry for <em>item</em> in <a class="tref internalDFN" title="memory" href="#dfn-memory">memory</a>, then let <em>subject</em> be the subject of
        that entry. Otherwise, if <em>item</em> has a <a class="tref internalDFN" title="global_identifier" href="#dfn-global_identifier">global identifier</a> and that
        <a class="tref internalDFN" title="global_identifier" href="#dfn-global_identifier">global identifier</a> is an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>, let <em>subject</em> be that
        <a class="tref internalDFN" title="global_identifier" href="#dfn-global_identifier">global identifier</a>. Otherwise, let <em>subject</em> be a new <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>.
      </li>
      <li>Add a mapping from <em>item</em> to <em>subject</em> in <a class="tref internalDFN" title="memory" href="#dfn-memory">memory</a></li>
      <li>
        For each <em>type</em> returned from
        <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
        of the element defining the <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
        <ol class="algorithm">
          <li>If <em>type</em> is an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>, generate the following triple:
            <dl class="triple">
              <dt>subject</dt>
              <dd><em>subject</em></dd>
              <dt>predicate</dt>
              <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</code></dd>
              <dt>object</dt>
              <dd><em>type</em> (as a <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a>)</dd>
            </dl>
          </li>
        </ol>
      </li>
      <li>
        Set <em>type</em> to the first value returned from
        <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
        of the element defining the <a class="tref internalDFN" title="item" href="#dfn-item">item</a>.
      </li><li>
        If <em>type</em> is not an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>, set it to <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> from the
        <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">Evaluation Context</a> if not empty.
      </li>
      <li>If the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains a <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a> that is a character for character match of <em>type</em>
        up to the length of the <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>, set <em>vocab</em> as that <a class="tref internalDFN" title="uri_prefix" href="#dfn-uri_prefix">URI prefix</a>.
      </li><li>Otherwise, if type is not empty, construct <em>vocab</em> by removing everything following the last
        SOLIDUS U+002F (&quot;/&quot;) or NUMBER SIGN U+0023 (&quot;#&quot;) from <em>type</em>.</li>
      <li>Update <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">evaluation context</a> setting <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a> to <em>vocab</em>.</li> 
      <li>
        Set <em>property list</em> to an empty array mapping properties to one or more
        <em>value</em>s as established below.
      </li>
      <li>
        For each element <em>element</em> that has one or more <a class="tref internalDFN" title="property_names" href="#dfn-property_names">property names</a> and is one of the
        <a class="tref internalDFN" title="item_properties" href="#dfn-item_properties">properties of the item</a> <em>item</em>, in the order those elements
        are given by the algorithm that returns the <a class="tref internalDFN" title="item_properties" href="#dfn-item_properties">properties of the item</a>,
        run the following substep:
        <ol class="algorithm">
          <li>
            For each <em>name</em> in the element's <a class="tref internalDFN" title="property_names" href="#dfn-property_names">property names</a>, run the following substeps:
            <ol class="algorithm">
              <li>
                Let <em>context</em> be a copy of <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">evaluation context</a> with <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> set
                to <em>type</em>.
              </li><li>
                Let <em>predicate</em> be the result of <a href="#generate-predicate-uri">generate predicate URI</a>
                using <em>context</em> and <em>name</em>.
                 Update <em>context</em> by setting <a class="tref internalDFN" title="current_name" href="#dfn-current_name">current name</a> to <em>predicate</em>.
              </li>
              <li>
                Let <em>value</em> be the <a class="tref internalDFN" title="property_value" href="#dfn-property_value">property value</a> of <em>element</em>.
              </li>
              <li>
                If <em>value</em> is an <a class="tref internalDFN" title="item" href="#dfn-item">item</a>, then <a href="#generate-the-triples">generate the
                triples</a> for <em>value</em> using <em>context</em>. Replace <em>value</em> by the subject returned
                from those steps.
              </li>
              <li>
                Add <em>value</em> to <em>property list</em> for <em>predicate</em>.
              </li>
            </ol>
          </li>
        </ol>
      </li>
      <li>
        For each <em>predicate</em> in <em>property list</em>:
        <ol class="algorithm">
          <li><a href="#generate-property-values">Generate property values</a> <em>subject</em>, <em>predicate</em> and
            the list of values associated with <em>predicate</em> from <em>property list</em> as <em>values</em>.
          </li>
        </ol>
      </li>
      <li>Return <em>subject</em></li>
    </ol>
  </div>
  
  <div id="generate-predicate-uri" class="section">
    <h3><span class="secno">4.4 </span>Generate Predicate URI</h3>
    <p>Predicate URI generation makes use of <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a>, <a class="tref internalDFN" title="current_name" href="#dfn-current_name">current name</a>,
      and <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a> from an <a class="tref internalDFN" title="evaluation_context" href="#dfn-evaluation_context">evaluation context</a> <em>context</em>
      along with <em>name</em>.</p>

    <ol class="algorithm">
      <li>If <em>name</em> is an <a class="tref internalDFN" title="absolute_url" href="#dfn-absolute_url">absolute URL</a>, return <em>name</em>
        as a <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a>.</li>
      <li>If <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> from <em>context</em> is null, there can be no <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a>.        
        Return the <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> that is the <a class="tref internalDFN" title="document_base" href="#dfn-document_base">document base</a> with its <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.5">fragment</a></cite> set to the <a class="tref internalDFN" title="fragment-escape" href="#dfn-fragment-escape">fragment-escape</a>d value
        of <em>name</em><p></p>
        <div class="note">
          This rule is intended to allow for a the case where no type is set, and therefore there is no
          vocabulary from which to extract rules. For example, if there is a <a class="tref internalDFN" title="document_base" href="#dfn-document_base">document base</a> of
          <code>http://example.org/doc</code> and an <a class="aref internalDFN" title="itemprop" href="#dfn-itemprop">@itemprop</a> of 'title', a URI will be constructed
          to be <code>http://example.org/doc#title</code>.
        </div>
      </li>
      <li>Otherwise, if <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a> from <em>context</em> is not null
        and <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> has an entry for <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a> having a
        <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri">propertyURI</a> entry that is not null, set that as <em>scheme</em>. Otherwise,
        set <em>scheme</em> to <code>vocabulary</code>.</li>
      <li id="scheme-vocab">If <em>scheme</em> is <code>vocabulary</code> return the <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a> constructed
        by appending the <a class="tref internalDFN" title="fragment-escape" href="#dfn-fragment-escape">fragment-escape</a>d value of <em>name</em> to <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a>,
        separated by a U+0023 NUMBER SIGN character (#) unless the <a class="tref internalDFN" title="current_vocabulary" href="#dfn-current_vocabulary">current vocabulary</a> ends
        with either a U+0023 NUMBER SIGN character (#) or SOLIDUS U+002F (/).</li>
      <li id="scheme-context">If <em>scheme</em> is <code>contextual</code>, return the <a class="tref internalDFN" title="uri_reference" href="#dfn-uri_reference">URI reference</a>
        constructed as follows:
        <ol class="algorithm">
          <li>Let <em>s</em> be <a class="tref internalDFN" title="current_type" href="#dfn-current_type">current type</a> from <em>context</em>.</li>
          <li>If <code>http://www.w3.org/ns/md?type=</code> is a prefix of <em>s</em>,
            return the concatenation of <em>s</em>, a U+002E FULL STOP character (.) and
            the <a class="tref internalDFN" title="fragment-escape" href="#dfn-fragment-escape">fragment-escape</a>d value of <em>name</em>.
          </li>
          <li>Otherwise, return the concatenation of <code>http://www.w3.org/ns/md?type=</code>,
            the <a class="tref internalDFN" title="fragment-escape" href="#dfn-fragment-escape">fragment-escape</a>d value of <em>s</em>, the string <code>&amp;prop=</code>,
            and the <a class="tref internalDFN" title="fragment-escape" href="#dfn-fragment-escape">fragment-escape</a>d value of <em>name</em>.
          </li>
        </ol>
      </li>
    </ol>
  </div>
  
  <div id="generate-property-values" class="section">
    <h3><span class="secno">4.5 </span>Generate Property Values</h3>
    <p>Property value serialization makes use of <em>subject</em>, <em>predicate</em> and <em>values</em>.</p>

    <ol class="algorithm">
      <li>If the <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains a URI prefix that is a character for character match of
        <em>predicate</em> up to the length of the URI prefix, set <em>vocab</em> as that URI prefix.
         Otherwise set <em>vocab</em> to null.</li>
      <li>If <em>vocab</em> is not null
        and <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> has an entry for <em>vocab</em> that is a JSON Object, let
        <em>registry object</em> be that value. Otherwise set <em>registry object</em> to null.</li>
      <li>If <em>registry object</em> is not null and <em>registry object</em> contains key
        <a class="tref internalDFN" title="properties" href="#dfn-properties"><code>properties</code></a>
        which has a JSON Object value, let <em>properties</em> be that value. Otherwise, set <em>properties</em>
        to null.</li>
      <li>If <em>properties</em> is not null, and <em>properties</em> contains a key, which after
        <a href="#generate-predicate-uri">Generate Predicate URI</a> expansion has a value which is a JSON Object, let
        <em>property override</em> be that value. Otherwise, set <em>property override</em> to null.</li>
      <li>If <em>property override</em> contains the key
        <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a>, set that as <em>method</em>.</li>
      <li>Otherwise, if <em>registry object</em> con  contains the key
        <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a>, set that as <em>method</em>.</li>
      <li>Otherwise, set <em>method</em> to <code>unordered</code>.</li>
      <li id="values-unordered">If <em>method</em> is <code>unordered</code>,
        for each <em>value</em> in <em>values</em>, generate the following triple:
        <dl class="triple">
          <dt>subject</dt>
          <dd><em>subject</em></dd>
          <dt>predicate</dt>
          <dd><em>predicate</em></dd>
          <dt>object</dt>
          <dd><em>value</em></dd>
        </dl>
      </li>
      <li id="values-list">Otherwise, if <em>method</em> is <code>list</code>:
        <ol class="algorithm">
          <li>Set <em>value</em> to the value returned from <a href="#generate-collection">generate an RDF
            Collection</a>.
          </li>
          <li>
            Generate the following triple:
            <dl class="triple">
              <dt>subject</dt>
              <dd><em>subject</em></dd>
              <dt>predicate</dt>
              <dd><em>predicate</em></dd>
              <dt>object</dt>
              <dd><em>value</em></dd>
            </dl>
          </li>
        </ol>
      </li>
    </ol>
  </div>

  <div id="generate-collection" class="section">
    <h3><span class="secno">4.6 </span>Generate RDF Collection</h3>
    <p>
      An <dfn title="rdf_collection" id="dfn-rdf_collection">RDF Collection</dfn> is a mechanism for defining ordered sequences of objects in RDF (See <cite><a href="http://www.w3.org/TR/rdf-syntax/#collections">RDF Collections</a></cite> in
      [<cite><a class="bibref" rel="biblioentry" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>]). As the RDF data-model is that of an unordered graph, a linking method using properties
      <code>rdf:first</code> and <code>rdf:next </code>is required to be able to specify a particular order.
    </p>
    <p>
      In the microdata to RDF mapping, <a class="tref internalDFN" title="rdf_collection" href="#dfn-rdf_collection">RDF Collection</a>s are used when an item has more than one value
      associated with a given property to ensure that the original document order is maintained. The following
      procedure should be used to generate triples when an <a class="tref internalDFN" title="item" href="#dfn-item">item</a> property has more than one value
      (contained in <em>list</em>):
    </p>
    <ol class="algorithm">
      <li>
        Create a new array <em>array</em> containing a <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a> for every value in <em>list</em>.
      </li>
      <li>
        For each pair of <em>bnode</em> from <em>array</em> and <em>value</em> from <em>list</em> the following
        triple is generated:
        <dl class="triple">
          <dt>subject</dt>
          <dd><em>bnode</em></dd>
          <dt>predicate</dt>
          <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#first</code></dd>
          <dt>object</dt>
          <dd><em>value</em></dd>
        </dl>
      </li>
      <li>
        For each <em>bnode</em> in <em>array</em> the following triple is generated:
        <dl class="triple">
          <dt>subject</dt>
          <dd><em>bnode</em></dd>
          <dt>predicate</dt>
          <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#rest</code></dd>
          <dt>object</dt>
          <dd>
            next <em>bnode</em> in <em>array</em> or, if that does not exist,
            <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#nil</code>
          </dd>
        </dl>
      </li>
      <li>
        Return the first <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a> from <em>array</em>.
      </li>
    </ol>
  </div>
</div>

<div class="appendix informative section" id="markup-examples">

<!-- OddPage -->
<h2><span class="secno">A. </span>Markup Examples</h2><p><em>This section is non-normative.</em></p>

<p>The microdata example below expresses book information as an FRBR Work item.</p>

<pre class="example">&lt;dl itemscope
    itemtype=&quot;http://purl.org/vocab/frbr/core#Work&quot;
    itemid=&quot;http://books.example.com/works/45U8QJGZSQKDH8N&quot;
    lang=&quot;en&quot;&gt;
 &lt;dt&gt;Title&lt;/dt&gt;
 &lt;dd&gt;&lt;cite itemprop=&quot;http://purl.org/dc/terms/title&quot;&gt;Just a Geek&lt;/cite&gt;&lt;/dd&gt;
 &lt;dt&gt;By&lt;/dt&gt;
 &lt;dd&gt;&lt;span itemprop=&quot;http://purl.org/dc/terms/creator&quot;&gt;Wil Wheaton&lt;/span&gt;&lt;/dd&gt;
 &lt;dt&gt;Format&lt;/dt&gt;
 &lt;dd itemprop=&quot;http://purl.org/vocab/frbr/core#realization&quot;
     itemscope
     itemtype=&quot;http://purl.org/vocab/frbr/core#Expression&quot;
     itemid=&quot;http://books.example.com/products/9780596007683.BOOK&quot;&gt;
  &lt;link itemprop=&quot;http://purl.org/dc/terms/type&quot; href=&quot;http://books.example.com/product-types/BOOK&quot;&gt;
  Print
 &lt;/dd&gt;
 &lt;dd itemprop=&quot;http://purl.org/vocab/frbr/core#realization&quot;
     itemscope
     itemtype=&quot;http://purl.org/vocab/frbr/core#Expression&quot;
     itemid=&quot;http://books.example.com/products/9780596802189.EBOOK&quot;&gt;
  &lt;link itemprop=&quot;http://purl.org/dc/terms/type&quot; href=&quot;http://books.example.com/product-types/EBOOK&quot;&gt;
  Ebook
 &lt;/dd&gt;
&lt;/dl&gt;</pre>

<p>Assuming that <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains a an entry for <code>http://purl.org/vocab/frbr/core#</code>
  with <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  this is equivalent to the following Turtle:</p>
<pre class="example">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
@prefix frbr: &lt;http://purl.org/vocab/frbr/core#&gt; .

&lt;&gt; md:item (&lt;http://books.example.com/works/45U8QJGZSQKDH8N&gt;) .

&lt;http://books.example.com/works/45U8QJGZSQKDH8N&gt; a frbr:Work ;
  dc:creator &quot;Wil Wheaton&quot;@en ;
  dc:title &quot;Just a Geek&quot;@en ;
  frbr:realization &lt;http://books.example.com/products/9780596007683.BOOK&gt;,
    &lt;http://books.example.com/products/9780596802189.EBOOK&gt; .

&lt;http://books.example.com/products/9780596007683.BOOK&gt; a frbr:Expression ;
  dc:type &lt;http://books.example.com/product-types/BOOK&gt; .

&lt;http://books.example.com/products/9780596802189.EBOOK&gt; a frbr:Expression ;
  dc:type &lt;http://books.example.com/product-types/EBOOK&gt; .</pre>

<p>The following snippet of HTML has microdata for two people with the same address. This illustrates two
  <a class="tref internalDFN" title="item" href="#dfn-item">item</a>s referencing a third item, and how only a single RDF resource definition is created
  for that third item.</p>
<pre class="example">&lt;p&gt;
 Both
 &lt;span itemscope=&quot;&quot; itemtype=&quot;http://microformats.org/profile/hcard&quot; itemref=&quot;home&quot;&gt;
   &lt;span itemprop=&quot;fn&quot;
       &gt;&lt;span itemprop=&quot;n&quot; itemscope=&quot;&quot;
       &gt;&lt;span itemprop=&quot;given-name&quot;&gt;Princeton&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;
  &lt;/span&gt;
 and
 &lt;span itemscope=&quot;&quot; itemtype=&quot;http://microformats.org/profile/hcard&quot; itemref=&quot;home&quot;&gt;
   &lt;span itemprop=&quot;fn&quot;
     &gt;&lt;span itemprop=&quot;n&quot; itemscope=&quot;&quot;
       &gt;&lt;span itemprop=&quot;given-name&quot;&gt;Trekkie&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;
  &lt;/span&gt;
 live at
 &lt;span id=&quot;home&quot; itemprop=&quot;adr&quot; itemscope=&quot;&quot;&gt;
   &lt;span itemprop=&quot;street-address&quot;&gt;Avenue Q&lt;/span&gt;.
 &lt;/span&gt;
&lt;/p&gt;</pre>

<p>Assuming that <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains a an entry for <code>http://microformats.org/profile/hcard</code>
  with <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  it generates these triples expressed in Turtle:</p>

<pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
@prefix hcard: &lt;http://microformats.org/profile/hcard#&gt; .

&lt;&gt; md:item (
  [ a &lt;http://microformats.org/profile/hcard&gt;;
    hcard:fn &quot;Princeton&quot;;
    hcard:n [ hcard:given-name &quot;Princeton&quot; ];
    hcard:adr _:a
  ]
  [ a &lt;http://microformats.org/profile/hcard&gt;;
    hcard:fn &quot;Trekkie&quot;;
    hcard:n [ hcard:given-name &quot;Trekkie&quot; ];
    hcard:adr _:a
  ]) .

_:a hcard:street-address &quot;Avenue Q&quot; .</pre>

<p>The following snippet of HTML has microdata for a playlist, and illustrates overriding a property
  to place elements in an RDF Collection:</p>
<pre class="example">&lt;div itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicPlaylist&quot;&gt;
  &lt;span itemprop=&quot;name&quot;&gt;Classic Rock Playlist&lt;/span&gt;
  &lt;meta itemprop=&quot;numTracks&quot; content=&quot;2&quot;/&gt;
  &lt;p&gt;Including works by
    &lt;span itemprop=&quot;byArtist&quot;&gt;Lynard Skynard&lt;/span&gt; and
    &lt;span itemprop=&quot;byArtist&quot;&gt;AC/DC&lt;/span&gt;&lt;/p&gt;.

  &lt;div itemprop=&quot;tracks&quot; itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicRecording&quot;&gt;
    1.&lt;span itemprop=&quot;name&quot;&gt;Sweet Home Alabama&lt;/span&gt; -
    &lt;span itemprop=&quot;byArtist&quot;&gt;Lynard Skynard&lt;/span&gt;
    &lt;link href=&quot;sweet-home-alabama&quot; itemprop=&quot;url&quot; /&gt;
   &lt;/div&gt;

  &lt;div itemprop=&quot;tracks&quot; itemscope=&quot;&quot; itemtype=&quot;http://schema.org/MusicRecording&quot;&gt;
    2.&lt;span itemprop=&quot;name&quot;&gt;Shook you all Night Long&lt;/span&gt; -
    &lt;span itemprop=&quot;byArtist&quot;&gt;AC/DC&lt;/span&gt;
    &lt;link href=&quot;shook-you-all-night-long&quot; itemprop=&quot;url&quot; /&gt;
  &lt;/div&gt;
&lt;/div&gt;</pre>

<p>Assuming that <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> contains a an entry for <code>http://schema.org/</code>
  with <a class="tref internalDFN" title="propertyuri" href="#dfn-propertyuri"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> set to <code>unordered</code> with the properties
  <code>track</code> and <code>byArtist</code> having <a class="tref internalDFN" title="multiplevalues" href="#dfn-multiplevalues"><code>multipleValues</code></a> set to <code>list</code>,
  it generates these triples expressed in Turtle:</p>

<pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
@prefix schema: &lt;http://schema.org/&gt; .

&lt;&gt; md:item ([ a schema:MusicPlaylist;
  schema:name &quot;Classic Rock Playlist&quot;;
  schema:byArtist (&quot;Lynard Skynard&quot; &quot;AC/DC&quot;);
  schema:numTracks &quot;2&quot;;
  schema:tracks (
    [ a schema:MusicRecording;
      schema:byArtist (&quot;Lynard Skynard&quot;);;
      schema:name &quot;Sweet Home Alabama&quot;;
      schema:url &lt;sweet-home-alabama&gt;]
    [ a schema:MusicRecording;
      schema:byArtist (&quot;AC/DC&quot;);;
      schema:name &quot;Shook you all Night Long&quot;;
      schema:url &lt;shook-you-all-night-long&gt;]
  )]); .</pre>

</div>

<div class="appendix informative section" id="example-registry">
  
<!-- OddPage -->
<h2><span class="secno">B. </span>Example <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a></h2><p><em>This section is non-normative.</em></p>
  <p>The following is an example <a class="tref internalDFN" title="registry" href="#dfn-registry">registry</a> in JSON format.</p>

  <pre class="example">{
  &quot;http://schema.org/&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    &quot;multipleValues&quot;: &quot;unordered&quot;,
    &quot;properties&quot;: {
      &quot;blogPosts&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;breadcrumb&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;byArtist&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;creator&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;episodes&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;events&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;founders&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;itemListElement&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;musicGroupMember&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;performerIn&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;performers&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;producer&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;recipeInstructions&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;seasons&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;subEvents&quot;: {&quot;multipleValues&quot;: &quot;list&quot;},
      &quot;tracks&quot;: {&quot;multipleValues&quot;: &quot;list&quot;}
    }
  },
  &quot;http://microformats.org/profile/hcard&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    &quot;multipleValues&quot;: &quot;unordered&quot;
  },
  &quot;http://microformats.org/profile/hcalendar#&quot;: {
    &quot;propertyURI&quot;:    &quot;vocabulary&quot;,
    &quot;multipleValues&quot;: &quot;unordered&quot;,
    &quot;properties&quot;: {
      &quot;categories&quot;: {&quot;multipleValues&quot;: &quot;list&quot;}
    }
  },
  &quot;http://n.whatwg.org/work&quot;: {
    &quot;propertyURI&quot;:    &quot;contextual&quot;,
    &quot;multipleValues&quot;: &quot;list&quot;
  }
}</pre>
<p></p>

<div class="appendix informative section" id="acknowledgements">
  <h3><span class="secno">B.1 </span>Acknowledgements</h3><p><em>This section is non-normative.</em></p>
  <p>Thanks to Richard Cyganiak for property URI and vocabulary terminology and the general excellent
    consideration of practical problems in generating RDF from microdata.</p>
</div>



</div><div id="references" class="appendix section">
<!-- OddPage -->
<h2><span class="secno">C. </span>References</h2><div id="normative-references" class="section"><h3><span class="secno">C.1 </span>Normative references</h3><dl class="bibliography"><dt id="bib-HTML5">[HTML5]</dt><dd>Ian Hickson; David Hyatt. <a href="http://www.w3.org/TR/html5"><cite>HTML5.</cite></a> 25 May 2011. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/html5">http://www.w3.org/TR/html5</a> 
</dd><dt id="bib-MICRODATA">[MICRODATA]</dt><dd><cite><a href="http://dev.w3.org/html5/md/">HTML Microdata</a></cite> Ian Hickson Editor. World Wide Web Consortium (work in progress). 18 November 2011. This edition of the HTML Microdata specification is http://dev.w3.org/html5/md/. The <a href="http://dev.w3.org/html5/md/">latest edition of HTML Microdata</a> is available at http://www.w3.org/TR/microdata/
</dd><dt id="bib-RDF-CONCEPTS">[RDF-CONCEPTS]</dt><dd>Graham Klyne; Jeremy J. Carroll. <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210"><cite>Resource Description Framework (RDF): Concepts and Abstract Syntax.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-concepts-20040210">http://www.w3.org/TR/2004/REC-rdf-concepts-20040210</a> 
</dd><dt id="bib-RDF-SCHEMA">[RDF-SCHEMA]</dt><dd>Dan Brickley; Ramanathan V. Guha. <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210"><cite>RDF Vocabulary Description Language 1.0: RDF Schema.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210">http://www.w3.org/TR/2004/REC-rdf-schema-20040210</a> 
</dd><dt id="bib-RFC3986">[RFC3986]</dt><dd>T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifier (URI): Generic Syntax.</cite></a> January 2005. Internet RFC 3986. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a> 
</dd></dl></div><div id="informative-references" class="section"><h3><span class="secno">C.2 </span>Informative references</h3><dl class="bibliography"><dt id="bib-RDF-SYNTAX-GRAMMAR">[RDF-SYNTAX-GRAMMAR]</dt><dd>Dave Beckett. <a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210"><cite>RDF/XML Syntax Specification (Revised).</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210">http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210</a> 
</dd></dl></div></div></body></html>