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   220 <body><div class="head">
   221   <p>
   223       <a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C"></a>
   225   </p>
   226   <h1 class="title" id="title">Microdata to RDF</h1>
   228     <h2 id="subtitle">Transformation from HTML+Microdata to RDF</h2>
   230   <h2 id="w3c-interest-group-note-09-october-2012"><abbr title="World Wide Web Consortium">W3C</abbr> Interest Group Note 09 October 2012</h2>
   231   <dl>
   233       <dt>This version:</dt>
   234       <dd><a href="http://www.w3.org/TR/2012/NOTE-microdata-rdf-20121009/">http://www.w3.org/TR/2012/NOTE-microdata-rdf-20121009/</a></dd>
   235       <dt>Latest published version:</dt>
   236       <dd><a href="http://www.w3.org/TR/microdata-rdf/">http://www.w3.org/TR/microdata-rdf/</a></dd>
   239       <dt>Latest editor's draft:</dt>
   240       <dd><a href="http://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/index.html">http://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/index.html</a></dd>
   246       <dt>Previous version:</dt>
   247       <dd><a href="http://www.w3.org/TR/2012/NOTE-microdata-rdf-20120308/">http://www.w3.org/TR/2012/NOTE-microdata-rdf-20120308/</a></dd>
   250     <dt>Editor:</dt>
   251     <dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, Kellogg Associates</dd>
   254       <dt>Authors:</dt>
   255       <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
   256 <dd><a href="http://greggkellogg.net/">Gregg Kellogg</a>, Kellogg Associates</dd>
   257 <dd><a href="http://www.jenitennison.com/">Jeni Tennison</a>, Independent</dd>
   258 <dd><a href="http://www.w3.org/People/Ivan/">Ivan Herman</a>, <a href="http://www.w3.org"><abbr title="World Wide Web Consortium">W3C</abbr></a></dd>
   261   </dl>
   264     <p>
   266         This document is also available in this non-normative format: 
   268       <a href="diff-20120308.html">diff to previous version</a>
   269     </p>
   274       <p class="copyright">
   275         <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 
   276         2011-2012
   278         <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> 
   279         (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
   280         <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
   281         <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved.
   282         <abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
   283         <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and
   284         <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.
   285       </p>
   288   <hr>
   289 </div>
   290 <section id="abstract" class="introductory"><h2>Abstract</h2>
   291   <p>HTML microdata [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>] is an extension to HTML used to embed machine-readable data into HTML documents.
   292     Whereas the microdata specification describes a means of markup, the output format is JSON. This specification
   293     describes processing rules that may be used to extract RDF [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>] from an HTML document containing
   294     microdata.</p>
   295 </section><section id="sotd" class="introductory"><h2>Status of This Document</h2>
   299         <p>
   300           <em>This section describes the status of this document at the time of its publication. Other
   301           documents may supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and the latest revision
   302           of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports
   303           index</a> at http://www.w3.org/TR/.</em>
   304         </p>
   306 <p>This document is an experimental work in progress. The concepts described herein are intended to 
   307   provide guidance for a possible future Working Group chartered to provide a Recommendation
   308   for this transformation. As a consequence, implementers of this specification, either producers
   309   or consumers, should note that it may change prior to any possible publication as a Recommendation.</p>
   311 <p>This Working Draft is an update of the <a href="/TR/2012/NOTE-microdata-rdf-20120308/"><abbr title="World Wide Web Consortium">W3C</abbr>
   312 Interest Group Note</a>, published in March 2012. This update adds the 
   313 <a href="#vocab_expansion">Vocabulary Expansion</a> feature to the conversion algorithm, in response to the 
   314 evolution of vocabularies discussed on the <a href="/2001/sw/interest/webschema.html">Web Schemas Task Force</a> 
   315 of the <a href="/2001/sw/interest/">Semantic Web Interest Group</a> at <abbr title="World Wide Web Consortium">W3C</abbr>. The intention is to publish 
   316 this draft as a new version of the Interest Group Note after gathering and incorporating community input.
   317 </p> 
   319         <p>
   320           This document was published by the <a href="http://www.w3.org/2001/sw/interest/">Semantic Web Interest Group</a> as an Interest Group Note.
   322           If you wish to make comments regarding this document, please send them to 
   323           <a href="mailto:semantic-web@w3.org">semantic-web@w3.org</a> 
   324           (<a href="mailto:semantic-web-request@w3.org?subject=subscribe">subscribe</a>,
   325           <a href="http://lists.w3.org/Archives/Public/semantic-web/">archives</a>).
   328           All feedback is welcome.
   329         </p>
   331           <p>
   332             Publication as an Interest Group Note does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr> Membership.
   333             This is a draft document and may be updated, replaced or obsoleted by other documents at 
   334             any time. It is inappropriate to cite this document as other than work in progress.
   335           </p>
   338         <p>
   343             The disclosure obligations of the Participants of this group are described in the 
   344             <a href="http://www.w3.org/2006/07/swig-charter#Ipr">charter</a>. 
   346         </p>
   351 </section><section id="toc"><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="#vocabulary-expansion" class="tocxref"><span class="secno">4. </span>Vocabulary Expansion</a><ul class="toc"><li class="tocline"><a href="#vocabulary-entailment" class="tocxref"><span class="secno">4.1 </span>Vocabulary Entailment</a></li><li class="tocline"><a href="#vocabulary-expansion-control-of-microdata-processors" class="tocxref"><span class="secno">4.2 </span>Vocabulary Expansion Control of Microdata Processors</a></li></ul></li><li class="tocline"><a href="#algorithm" class="tocxref"><span class="secno">5. </span>Algorithm</a><ul class="toc"><li class="tocline"><a href="#algorithm-terms" class="tocxref"><span class="secno">5.1 </span>Algorithm Terms</a></li><li class="tocline"><a href="#rdf-conversion-algorithm" class="tocxref"><span class="secno">5.2 </span>RDF Conversion Algorithm</a></li><li class="tocline"><a href="#generate-the-triples" class="tocxref"><span class="secno">5.3 </span>Generate the triples</a></li><li class="tocline"><a href="#generate-predicate-uri" class="tocxref"><span class="secno">5.4 </span>Generate Predicate URI</a></li><li class="tocline"><a href="#generate-property-values" class="tocxref"><span class="secno">5.5 </span>Generate Property Values</a></li><li class="tocline"><a href="#generate-collection" class="tocxref"><span class="secno">5.6 </span>Generate RDF Collection</a></li></ul></li><li class="tocline"><a href="#testing" class="tocxref"><span class="secno">A. </span>Testing</a></li><li class="tocline"><a href="#markup-examples" class="tocxref"><span class="secno">B. </span>Markup Examples</a></li><li class="tocline"><a href="#example-registry" class="tocxref"><span class="secno">C. </span>Example <span class="formerLink">registry</span></a></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">D. </span>Acknowledgements</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">E. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">E.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">E.2 </span>Informative references</a></li></ul></li></ul></section>
   355 <section class="informative" id="introduction">
   356   <!--OddPage--><h2><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
   357   <p>This document describes a means of transforming HTML containing microdata into RDF. HTML Microdata [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]
   358     is an extension to HTML used to embed machine-readable data to HTML documents. This specification describes
   359     transformation directly to RDF [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>].</p>
   360   <div class="note"><div class="note-title"><span>Note</span></div><div class="">
   361     <p>There are a variety of ways in which a mapping from microdata to
   362       RDF might be configured to give a result that is closer to the required result for a particular vocabulary. This
   363       specification defines terms that can be used as hooks for vocabulary-specific behavior, which could be defined
   364       within a <a href="#dfn-registry" class="internalDFN">registry</a> or on an implementation-defined basis. However, the HTML Data TF recommends the
   365       adoption of a single method of mapping in which every vocabulary is treated as if:</p>
   366     <ul>
   367       <li><a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> is set to <code>vocabulary</code> </li>
   368       <li><a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> is set to <code>unordered</code></li>
   369     </ul>
   370     <p>For background on the trade-offs between these options, see 
   371       <a href="http://www.w3.org/wiki/Mapping_Microdata_to_RDF">http://www.w3.org/wiki/Mapping_Microdata_to_RDF</a>.</p>
   372   </div></div>
   373 <section class="informative" id="background">
   374   <h3><span class="secno">1.1 </span>Background</h3><p><em>This section is non-normative.</em></p>
   375   <p>Microdata [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>] is a way of embedding data in HTML documents
   376     using attributes. The HTML DOM is extended to provide an API for
   377     accessing microdata information, and the microdata specification
   378     defines how to generate a JSON representation from microdata markup.</p>
   380   <p>Mapping microdata to RDF enables consumers to merge data expressed
   381     in other RDF-based formats with microdata. It facilitates the use of
   382     RDF vocabularies within microdata, and enables microdata to be used
   383     with the full RDF toolchain. Some use cases for this mapping are
   384     described in <a href="#use-cases">Section 1.2</a> below.</p>
   386   <p>Microdata's data model does not align neatly with RDF.</p>
   387   <ul>
   388    <li>Non-URL microdata properties are disambiguated based on microdata
   389      <a href="#dfn-item-type" class="internalDFN">item type</a>; an <a href="#dfn-item" class="internalDFN">item</a> with the type <code>http://example.org/Cat</code> can have
   390      both the property <code>color</code> and the property <code>http://example.org/color</code>,
   391      and these properties are semantically distinct under microdata. In
   392      RDF, all properties have IRIs.</li>
   394    <li>When an item has multiple properties with the same name, the values are
   395      always ordered; in RDF, property values are unordered unless they
   396      are explicitly listed in an <a href="#dfn-rdf-collection" class="internalDFN">RDF Collection</a>.</li>
   398    <li>A value in microdata is always a simple string which is interpreted
   399      by the consuming application. In RDF, values can be tagged with a
   400      datatype or a language. According to the microdata specification, the
   401      HTML context of microdata markup should not change how microdata is
   402      interpreted, so although element names and HTML <code>@lang</code> attributes could
   403      be used to provide datatype and language information for RDF data, this
   404      would be contrary to the microdata specification.</li>
   405   </ul>
   407    <p>Thus, in some places the needs of RDF consumers violate requirements of
   408      the microdata specification. This specification highlights where such
   409      violations occur and the reasons for them.</p>
   411    <p>This specification allows for 
   412      <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a>-specific rules that affect the generation of property URIs and value serializations.
   413      This is facilitated by a <a href="#dfn-registry" class="internalDFN">registry</a> that associates URIs with specific rules based on matching
   414      <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a> values against registered URI prefixes do determine a vocabulary and potentially
   415      vocabulary-specific processing rules.</p>
   417    <p>This specification also assumes that consumers of RDF generated from
   418      microdata may have to process the results in order to, for example,
   419      assign appropriate datatypes to <a href="#dfn-property-value" class="internalDFN">property value</a>s.</p>
   420 </section>
   422 <section class="informative" id="use-cases">
   423   <h3><span class="secno">1.2 </span>Use Cases</h3><p><em>This section is non-normative.</em></p>
   424   <p>During the period of the task force, a number of use cases were put forth for the use of microdata
   425     in generating RDF:</p>
   426   <ul>
   427     <li>Semantic search engines such as <a href="http://sindice.com/">Sindice</a> use RDF as their backend data model.
   428       They want to gather information expressed using microdata alongside information expressed in RDF-based formats
   429       and make it available to others to use, as a service. In these cases, the ultimate consumer, who will need to
   430       understand the vocabularies used within the microdata, is the program or person who pulls out data from Sindice.
   431       Sindice needs to retain the distinctions in the original microdata (e.g. ordering of items) and might not have
   432       built-in knowledge about the <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a> of interest to the ultimate consumer. In this case, the ultimate consumer
   433       is likely to have to map/validate/handle errors in the data they get from Sindice.</li>
   434     <li>A consumer such as <a href="http://openelectiondata.org">openelectiondata.org</a> wants to support
   435       microdata-based markup of their <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a> as well as RDFa-based markup, both going into an RDF-based data store.
   436       They want to use an off-the-shelf tool to extract the microdata. They want to configure the tool to give them the
   437       RDF that is appropriate for their known <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a>.</li>
   438     <li>A browser plugin that captures data for the user uses an RDF model as its backend store.
   439       Any time it encounters microdata on a page, it wants to pull that microdata into the store on the fly.</li>
   440     <li><a href="http://purl.org/goodrelations/">GoodRelations</a> properties do not take
   441       <a title="rdf collection">rdf:List</a> values; when they take
   442       multiple values they are unordered. The <code>rdfs:range</code> of a GoodRelations
   443       property indicates the datatype of the expected value, and GoodRelations
   444       processors will expect values to be cast to that type. Language
   445       information from the HTML needs to be captured as it is common that
   446       multiple values will be used to specify the same information in different
   447       languages.</li>
   448     <li><a href="http://schema.org/">Schema.org</a> has an 
   449       <a href="http://schema.org/docs/extension.html">extension mechanism</a> to allow authors to express information
   450       that is more detail than the pre-defined types, properties and enumerations. Property URIs are all in the same
   451       flat-namespace as types, but authors can add more detail by using a '/' after the type or property to provide
   452       more detail. For example, schema.org defines a <em>musicGroupMember</em> property having a URI of
   453       <code>http://schema.org/musicGroupMember</code>, and an author might express more detail through an ad-hoc
   454       sub-property <em>musicGroupMember/leadVocalist</em>, having the URI
   455       <code>http://schema.org/musicGroupMember/leadVocalist</code>.</li>
   456   </ul>
   457 </section>
   459 <section class="informative" id="issues">
   460   <h3><span class="secno">1.3 </span>Issues</h3><p><em>This section is non-normative.</em></p>
   461   <p>Decisions or open issues in the specification are tracked on the
   462     <a href="http://www.w3.org/2011/htmldata/track/issues">Task Force Issue Tracker</a>. These include the
   463     following:</p>
   464   <div class="issue"><div class="issue-title"><a href="http://www.w3.org/2011/htmldata/track/issues/1"><span>Issue 1</span></a></div><p class="">Vocabulary specific parsing for Microdata.
   465     This specification attempts to create generic
   466     rules for processing microdata with typical RDF vocabularies.
   467     A <a href="#dfn-registry" class="internalDFN">registry</a> allows
   468     for exceptions to the default processing rules for certain well-known vocabularies.</p></div>
   469   <div class="issue"><div class="issue-title"><a href="http://www.w3.org/2011/htmldata/track/issues/2"><span>Issue 2</span></a></div><p class="">Should Microdata-RDF generate XMLLiteral values.
   470     This issue has been closed with no change
   471     as this would violate microdata's data model.</p></div>
   472   <div class="issue"><div class="issue-title"><a href="http://www.w3.org/2011/htmldata/track/issues/3"><span>Issue 3</span></a></div><p class="">Should the <a href="#dfn-registry" class="internalDFN">registry</a> allow property datatype specification.
   473     The consensus is that datatypes are only derived from HTML semantics, so that only &lt;time&gt; values have a datatype other than plain.</p></div>
   474   <div class="issue"><div class="issue-title"><a href="http://www.w3.org/2011/htmldata/track/issues/4"><span>Issue 4</span></a></div><p class="">Should the <a href="#dfn-registry" class="internalDFN">registry</a> allow a <a href="#dfn-name" class="internalDFN">name</a> or URL
   475     to be used as an alias for <a class="aref internalDFN" href="#dfn-itemid">itemid</a>.</p></div>
   477   <p>The purpose of this specification is to provide input to a future working group that can make decisions
   478     about the need for a <a href="#dfn-registry" class="internalDFN">registry</a> and the details of processing. Among the options investigated by
   479     the Task Force are the following:</p>
   480   <ul>
   481     <li>Property URI generation using the original microdata specification with a base URI and
   482       <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.5">fragment</a></cite> made up of the in-scope <a href="#dfn-item-type" class="internalDFN">item
   483       type</a> and <a href="#dfn-properties" class="internalDFN">properties</a>.</li>
   484     <li>Vocabulary-based URI generation, where the <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a> is determined from the
   485       in-scope <a href="#dfn-item-type" class="internalDFN">item type</a>, either through an algorithmic modification of the type URL or by matching the
   486       URL against a <a href="#dfn-registry" class="internalDFN">registry</a>. The vocabulary URI is then used to generate property URIs in a namespace
   487       parallel to the type URI.</li>
   488     <li>When there are multiple <a href="#dfn-top-level-item" class="internalDFN">top-level item</a>s in a document, place items in an RDF Collection.
   489       Alternatively, simply list the items as multiple values, or do not generate an
   490       <code>http://www.w3.org/ns/md#item</code> mapping at all.</li>
   491     <li>When an item has multiple values for a given <a href="#dfn-property" class="internalDFN">property</a>, place the values in an RDF Collection.
   492       Alternatively, do not use collections, use an alternative such as <code>rdf:Seq</code>, or place all values,
   493       whether or not multiple, into some form of collection.</li>
   494   </ul>
   495   <p>More examples and explanatory information are available in [<cite><a class="bibref" href="#bib-MICRODATA-RDF-SUPPLEMENT">MICRODATA-RDF-SUPPLEMENT</a></cite>], which may
   496     be updated from time to time.</p>
   497 </section>
   498 </section>
   500 <section id="attributes-and-syntax">
   501   <!--OddPage--><h2><span class="secno">2. </span>Attributes and Syntax</h2>
   502   <p>
   503     The microdata specification [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>] defines a number of attributes and the way in which those
   504     attributes are to be interpreted. The
   505     <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">microdata DOM API</a></cite>
   506     provides methods and attributes for retrieving microdata from the HTML DOM.</p>
   507   <p>For reference, attributes used for specifying and retrieving HTML microdata are referenced here:</p>
   508   <dl>
   509     <dt><dfn class="adef" id="dfn-itemid">itemid</dfn></dt><dd>
   510       An attribute containing a URL used to identify the subject of triples associated with this <a href="#dfn-item" class="internalDFN">item</a>.
   511       (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemid">Items</a></cite>
   512       in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
   513     </dd>
   514     <dt><dfn class="adef" id="dfn-itemprop">itemprop</dfn></dt><dd>
   515       An attribute used to identify one or more <a href="#dfn-name" class="internalDFN">name</a>s of an <a href="#dfn-item" class="internalDFN">item</a>s. An <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>
   516       contains a space separated list of <dfn id="dfn-name">name</dfn>s which may either by <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>s or terms
   517       associated with the type of the <a href="#dfn-item" class="internalDFN">item</a> as defined by the referencing <a href="#dfn-item" class="internalDFN">item</a>'s
   518       <a href="#dfn-item-type" class="internalDFN">item type</a>.
   519       (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#names:-the-itemprop-attribute">Items</a></cite>
   520       in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
   521     </dd>
   522     <dt><dfn class="adef" id="dfn-itemref">itemref</dfn></dt><dd>
   523       An additional attribute on an element that references additional elements containing property
   524       definitions to be applied to the referencing <a href="#dfn-item" class="internalDFN">item</a>.
   525       (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemref">Items</a></cite>
   526       in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
   527     </dd>
   528     <dt><dfn class="adef" id="dfn-itemscope">itemscope</dfn></dt><dd>
   529       An boolean attribute identifying an element as an <a href="#dfn-item" class="internalDFN">item</a>.
   530       (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemscope">Items</a></cite>
   531       in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
   532     </dd>
   533     <dt><dfn class="adef" id="dfn-itemtype">itemtype</dfn></dt><dd>
   534       An additional attribute on an element used to specify one or more types of an <a href="#dfn-item" class="internalDFN">item</a>.
   535       The <dfn id="dfn-item-type">item type</dfn> of an <a href="#dfn-item" class="internalDFN">item</a> is the first value returned from
   536       <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
   537       on the element.
   538       The <a href="#dfn-item-type" class="internalDFN">item type</a> is also used to resolve non-URL <a href="#dfn-name" class="internalDFN">name</a>s to <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>s.
   539       Available through the
   540       <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite> as
   541       <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>.
   542       (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#attr-itemtype">Items</a></cite>
   543       in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
   544     </dd>
   545   </dl>
   546   <p>In RDF, it is common for people to shorten vocabulary terms via abbreviated URIs that use a 'prefix'
   547     and a 'reference'. throughout this document assume that the following vocabulary
   548     prefixes have been defined:</p>
   549   <table><tbody>
   550     <tr>
   551       <td>dc:</td>
   552       <td>http://purl.org/dc/terms/</td>
   553     </tr>
   555     <tr>
   556       <td>md:</td>
   557       <td>
   558         http://www.w3.org/ns/md#</td>
   559     </tr>
   561     <tr>
   562       <td>rdf:</td>
   563       <td>
   564         http://www.w3.org/1999/02/22-rdf-syntax-ns#</td>
   565     </tr>
   567     <tr>
   568       <td>rdf:</td>
   569       <td>
   570         http://www.w3.org/1999/02/22-rdf-syntax-ns#</td>
   571     </tr>
   573     <tr>
   574       <td>rdfa:</td>
   575       <td>
   576         http://www.w3.org/ns/rdfa#</td>
   577     </tr>
   579     <tr>
   580       <td>xsd:</td>
   581       <td>http://www.w3.org/2001/XMLSchema#</td>
   582     </tr>
   583   </tbody></table>
   584 </section>
   586 <section class="informative" id="vocabulary-registry">
   587   <!--OddPage--><h2><span class="secno">3. </span>Vocabulary Registry</h2><p><em>This section is non-normative.</em></p>
   588   <p>In a perfect world, all processors would be able to generate the same output for a given input
   589     without regards to the requirements of a particular <a href="#dfn-vocabulary" class="internalDFN">vocabulary</a>. However, microdata doesn't
   590     provide sufficient syntactic help in making these decisions. Different vocabularies have different
   591     needs.</p>
   592   <p>The registry is located at the namespace defined for microdata: <code>http://www.w3.org/ns/md</code> in
   593     a variety of formats.</p>
   594   <p>The <dfn id="dfn-registry">registry</dfn> associates a <dfn id="dfn-uri-prefix">URI prefix</dfn> with one or more key-value pairs denoting
   595   processor behavior. A hypothetical JSON representation of such a registry might be the following:</p>
   596 <div class="example"><div class="example-title"><span>Example 1</span></div><pre class="example">{
   597   "http://schema.org/": {
   598     "propertyURI":    "vocabulary",
   599     "multipleValues": "unordered",
   600     "properties": {
   601       "tracks": {"multipleValues": "list"}
   602     }
   603   },
   604   "http://microformats.org/profile/hcard": {
   605     "propertyURI":    "vocabulary",
   606     "multipleValues": "list",
   607     "properties" {
   608       "url": {"multipleValues": "unordered"}
   609     }
   610   }
   611 }</pre></div>
   612   <p>This structure associates mappings for two URIs, <code>http://schema.org/</code> and
   613     <code>http://microformats.org/profile/hcard</code>. Items having an <a href="#dfn-item-type" class="internalDFN">item type</a> with a <a href="#dfn-uri-prefix" class="internalDFN">URI
   614     prefix</a> from this <a href="#dfn-registry" class="internalDFN">registry</a> use the the rules described for that prefix within the scope of that
   615     <a href="#dfn-item-type" class="internalDFN">item type</a>. This mapping currently defines two rules: <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> and
   616     <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> with values to indicate specific behavior. It also allows overrides
   617     on a per-property basis; the <a href="#dfn-properties" class="internalDFN"><code>properties</code></a> key associates an individual <a href="#dfn-name" class="internalDFN">name</a>
   618     with overrides for default behavior.
   619     The interpretation of these
   620     rules is defined in the following sections. If an item has no <a href="#dfn-current-type" class="internalDFN">current type</a> or the
   621     <a href="#dfn-registry" class="internalDFN">registry</a> contains no <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> matching <a href="#dfn-current-type" class="internalDFN">current type</a>, a conforming
   622     processor <em class="rfc2119" title="must">must</em> use the default values defined for these rules.</p>
   623   <div class="note"><div class="note-title"><span>Note</span></div><p class="">The concept of a <a href="#dfn-registry" class="internalDFN">registry</a>, including a hypothetical format, location and updating rules
   624     is presented as an abstract concept useful for describing the function of a microdata processor.
   625     There are issues surrounding update
   626     frequency, URL naming, and how updates are authorized. This spec
   627     just considers the semantic content of such a <a href="#dfn-registry" class="internalDFN">registry</a> and how it can be used to affect processing without
   628     defining its representation or update policies.</p></div>
   630 <section class="informative" id="property-uri-generation">
   631   <h3><span class="secno">3.1 </span>Property URI Generation</h3><p><em>This section is non-normative.</em></p>
   632   <p>For <a href="#dfn-name" class="internalDFN">name</a>s which are not <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>s,
   633     the <dfn id="dfn-propertyuri"><code>propertyURI</code></dfn> rule defines the algorithm for generating an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>
   634     given an <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a> including a <a href="#dfn-current-type" class="internalDFN">current type</a>, <a href="#dfn-current-name" class="internalDFN">current name</a> and
   635     <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a>.</p>
   636   <p>The procedure for generating property URIs is defined in
   637     <a href="#generate-predicate-uri">Generate Predicate URI</a>.</p>
   638   <p>Possible values for <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> are the following:</p>
   639   <dl>
   640     <dt><code>contextual</code></dt><dd>
   641       The <code>contextual</code> URI generation scheme guarantees that generated property URIs are
   642       unique based on the value of <a href="#dfn-current-name" class="internalDFN">current name</a>. This is
   643       required as the microdata data model requires that <a href="#dfn-name" class="internalDFN">name</a>s are associated with specific
   644       items and do not have a global scope. (See <a href="#scheme-context">Step 5</a> in
   645       <a href="#generate-predicate-uri">Generate Predicate URI</a>).
   646       <div>
   647         <p>URI creation uses a base URI with query parameters to indicate the in-scope
   648           type and <a href="#dfn-name" class="internalDFN">name</a> list. Consider the following example:</p>
   649         <div class="example"><div class="example-title"><span>Example 2</span></div><pre class="example">&lt;span itemscope itemtype="http://microformats.org/profile/hcard"&gt;
   650   &lt;span itemprop="n" itemscope&gt;
   651     &lt;span itemprop="given-name"&gt;
   652       Princeton
   653     &lt;/span&gt;
   654   &lt;/span&gt;
   655 &lt;/span&gt;</pre></div>
   656         <p>The first <a href="#dfn-name" class="internalDFN">name</a> <em>n</em> generates the URI
   657           <code>http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop=n</code>.
   658           However, the included <a href="#dfn-name" class="internalDFN">name</a> <em>given-name</em> is included in untyped item.
   659           The inherited property URI is used to create a new property URI:
   660           <code>http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop=n.given-name</code>.</p>
   661         <p>This scheme is compatible with the needs of other RDF serialization formats such as
   662           RDF/XML [<cite><a class="bibref" href="#bib-RDF-SYNTAX-GRAMMAR">RDF-SYNTAX-GRAMMAR</a></cite>],
   663           which rely on <em>QNames</em> for expressing properties. For example, the generated property URIs
   664           can be split as follows:</p>
   665         <div class="example"><div class="example-title"><span>Example 3</span></div><pre class="example">&lt;rdf:Description xmlns:hcard="http://www.w3.org/ns/md?type=http://microformats.org/profile/hcard?prop="
   666                  rdf:type="http://microformats.org/profile/hcard"&gt;
   667   &lt;hcard:n&gt;
   668     &lt;rdf:Description&gt;
   669       &lt;hcard:n.given-name&gt;
   670         Princeton
   671       &lt;/hcard:n.given-name&gt;
   672     &lt;/rdf:Description&gt;
   673   &lt;/hcard:n&gt;
   674 &lt;/rdf:Description&gt;</pre></div>
   675         <p>Looking at another example:</p>
   676         <div class="example"><div class="example-title"><span>Example 4</span></div><pre class="example">&lt;div itemscope itemtype="http://schema.org/Person"&gt;
   677   &lt;h2 itemprop="name"&gt;Jeni&lt;/h2&gt;
   678 &lt;/div&gt;</pre></div>
   679         <p>This would generate <code>http://www.w3.org/ns/md?type=http://schema.org/Person&amp;prop=name</code>.</p>
   680       </div>
   681     </dd>
   682     <dt><code>vocabulary</code></dt><dd>
   683       The <code>vocabulary</code> URI generation scheme appends <a href="#dfn-name" class="internalDFN">name</a>s that are not
   684       <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>s to the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a>. When generating property URIs, if the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a>
   685       does not end with a '/' or '#', a '#' is appended to the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a>. (See <a href="#scheme-vocab">Step 4</a>
   686       in
   687       <a href="#generate-predicate-uri">Generate Predicate URI</a>.)
   688       <div>
   689         <p>URI creation uses a base URL with query parameters to indicate the in-scope
   690           type and <a href="#dfn-name" class="internalDFN">name</a> list. Consider the following example:</p>
   691         <div class="example"><div class="example-title"><span>Example 5</span></div><pre class="example">&lt;span itemscope itemtype="http://microformats.org/profile/hcard"&gt;
   692   &lt;span itemprop="n" itemscope&gt;
   693     &lt;span itemprop="given-name"&gt;
   694       Princeton
   695     &lt;/span&gt;
   696   &lt;/span&gt;
   697 &lt;/span&gt;</pre></div>
   698         <p>Given the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> <code>http://microformats.org/profile/hcard</code>, this
   699           would generate <code>http://microformats.org/profile/hcard#n</code> and
   700           <code>http://microformats.org/profile/hcard#given-name</code>. Note that the '#' is automatically
   701           added as a separator.</p>
   702         <p>Looking at another example:</p>
   703         <div class="example"><div class="example-title"><span>Example 6</span></div><pre class="example">&lt;div itemscope itemtype="http://schema.org/Person"&gt;
   704   &lt;h2 itemprop="name"&gt;Jeni&lt;/h2&gt;
   705 &lt;/div&gt;</pre></div>
   706         <p>Given the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> <code>http://schema.org/</code>,
   707           this would generate <code>http://schema.org/name</code>. Note that if the <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a>
   708           were <code>http://schema.org/Person/Teacher</code>, this would generate the same property URI.</p>
   709       </div>
   710     </dd>
   711   </dl>
   712   <p>If the <a href="#dfn-registry" class="internalDFN">registry</a> contains no match for <a href="#dfn-current-type" class="internalDFN">current type</a> implementations act as if
   713     there is a <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> made from the first <a class="aref internalDFN" 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
   714     [<cite><a class="bibref" href="#bib-RFC3986">RFC3986</a></cite>]).</p>
   715   <div class="note"><div class="note-title"><span>Note</span></div><p class="">Deconstructing the <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a> URL to create or identify a vocabulary URI
   716     is a violation of the microdata specification which is necessary to
   717     support the use of existing vocabularies designed for use with RDF, and
   718     shared or inherited properties within all vocabularies.</p></div>
   719   <p>The default value of <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> is <code>vocabulary</code>.</p>
   720   <div class="example"><div class="example-title"><span>Example 7</span></div><pre class="example">&lt;div itemscope itemtype="http://schema.org/Book"&gt;
   721   &lt;h2 itemprop="title"&gt;Just a Geek&lt;/h2&gt;
   722 &lt;/div&gt;</pre></div>
   723   <p>In this example, assuming no matching entry in the <a href="#dfn-registry" class="internalDFN">registry</a>,
   724     the <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> is constructed by removing the
   725     <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.3">last path segment</a></cite>, leaving the URI
   726     <code>http://schema.org/</code>. As there is no explicit <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a>,
   727     the default <code>vocabulary</code> is used, and the resulting property URI would be
   728     <code>http://schema.org/title</code>.</p>
   729 </section>
   731 <section class="informative" id="value-ordering">
   732   <h3><span class="secno">3.2 </span>Value Ordering</h3><p><em>This section is non-normative.</em></p>
   733   <p>For items having multiple values for a given <a href="#dfn-property" class="internalDFN">property</a>,
   734     the <dfn id="dfn-multiplevalues"><code>multipleValues</code></dfn> rule defines the algorithm for serializing these values.
   735     Microdata uses document order when generating <a href="#dfn-property-value" class="internalDFN">property value</a>s, as defined in
   736     <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite>
   737     as <code>element.itemValue</code>. However, many RDF vocabularies expect multiple values to be generated
   738     as triples sharing a common subject and predicate. In some cases, it may be useful to retain value ordering.</p>
   739   <p>The procedure for generating <a href="#dfn-property-value" class="internalDFN">property value</a>s is defined in
   740     <a href="#generate-property-values">Generate Property Values</a>.</p>
   741   <p>Possible values for <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> are the following:</p>
   742   <dl>
   743     <dt><code>unordered</code></dt><dd>
   744       Values are serialized without ordering using a common subject and predicate.
   745       (See <a href="#values-unordered">Step 7</a> in
   746       <a href="#generate-property-values">Generate Property Values</a>).
   747     </dd>
   748     <dt><code>list</code></dt><dd>
   749       Multi-valued <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>s are serialized using an <a href="#dfn-rdf-collection" class="internalDFN">RDF Collection</a>.
   750       (See <a href="#values-list">Step 8</a> in
   751       <a href="#generate-property-values">Generate Property Values</a>).
   752     </dd>
   753   </dl>
   754   <p>An example of how this might be specified in a <a href="#dfn-registry" class="internalDFN">registry</a> is the following:</p>
   755   <div class="example"><div class="example-title"><span>Example 8</span></div><pre class="example">{
   756   "http://schema.org/": {
   757     "propertyURI":    "vocabulary",
   758     <span class="diff">"multipleValues": "unordered"</span>
   759   },
   760   "http://microformats.org/profile/hcard": {
   761     "propertyURI":    "vocabulary",
   762     <span class="diff">"multipleValues": {"multipleValues": "list"}</span>
   763   }
   764 }</pre></div>
   765   <p>Additionally, some vocabularies may wish to specify this on a per-property basis. For example,
   766     within <code>http://schema.org/MusicPlaylist</code> the <code>tracks</code> property might depend on the order
   767     of values to to reproduce associated <code>MusicRecording</code> values.</p>
   768   <div class="example"><div class="example-title"><span>Example 9</span></div><pre class="example">{
   769  "http://schema.org/": {
   770    "propertyURI": "vocabulary",
   771    "multipleValues": "unordered"<span class="diff">,
   772    "properties": {
   773      "tracks": {"multipleValues": "list"}
   774    }</span>
   775  }
   776 }</pre></div>
   777   <p>The <dfn id="dfn-properties"><code>properties</code></dfn> key takes a JSON Object as a value, which in turn has keys for each
   778     property that is to be given alternate semantics. Each <a href="#dfn-name" class="internalDFN">name</a> is implicitly expanded to it's URI
   779     representation as defined in <a href="#generate-predicate-uri">Generate Predicate URI</a>, so that
   780     the behavior is the same whether or not the <a href="#dfn-name" class="internalDFN">name</a> is listed as an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>.</p>
   781   <p>The default value of <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> is <code>unordered</code>.</p>
   782   <div class="note"><div class="note-title"><span>Note</span></div><div class="">
   783     <p>An alternative mechanism would output <em>both</em> unordered and ordered values, to allow an application
   784     to choose the most useful representation. For example, consider the following:</p>
   785 <div class="example"><div class="example-title"><span>Example 10</span></div><pre class="example">&lt;div itemscope itemtype="http://schema.org/MusicPlaylist"&gt;
   786   &lt;span itemprop="name"&gt;Classic Rock Playlist&lt;/span&gt;
   787   &lt;meta itemprop="numTracks" content="2"/&gt;
   788   &lt;p&gt;Including works by
   789     &lt;span itemprop="byArtist"&gt;Lynard Skynard&lt;/span&gt; and
   790     &lt;span itemprop="byArtist"&gt;AC/DC&lt;/span&gt;&lt;/p&gt;.
   792   &lt;div itemprop="tracks" itemscope itemtype="http://schema.org/MusicRecording"&gt;
   793     1.&lt;span itemprop="name"&gt;Sweet Home Alabama&lt;/span&gt; -
   794     &lt;span itemprop="byArtist"&gt;Lynard Skynard&lt;/span&gt;
   795     &lt;link href="sweet-home-alabama" itemprop="url" /&gt;
   796    &lt;/div&gt;
   798   &lt;div itemprop="tracks" itemscope itemtype="http://schema.org/MusicRecording"&gt;
   799     2.&lt;span itemprop="name"&gt;Shook you all Night Long&lt;/span&gt; -
   800     &lt;span itemprop="byArtist"&gt;AC/DC&lt;/span&gt;
   801     &lt;link href="shook-you-all-night-long" itemprop="url" /&gt;
   802   &lt;/div&gt;
   803 &lt;/div&gt;</pre></div>
   804     <p>This might generate the following Turtle:</p>
   805 <div class="example"><div class="example-title"><span>Example 11</span></div><pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
   806 @prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
   807 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
   808 @prefix schema: &lt;http://schema.org/&gt; .
   810 &lt;&gt; md:item [
   811   a schema:MusicPlaylist;
   812     schema:name "Classic Rock Playlist";
   813     schema:byArtist ("Lynard Skynard" "AC/DC");
   814     schema:numTracks "2";
   815     schema:tracks _:track1, _:track2, (_:track1 _:track2)
   816   ];
   817   rdfa:usesVocabulary schema:
   818  .
   819 _:track1 a schema:MusicRecording;
   820   schema:byArtist ("Lynard Skynard");
   821   schema:name "Sweet Home Alabama";
   822   schema:url &lt;sweet-home-alabama&gt; .
   823 _:track2 a schema:MusicRecording;
   824   schema:byArtist ("AC/DC");
   825   schema:name "Shook you all Night Long";
   826   schema:url &lt;shook-you-all-night-long&gt; .</pre></div>
   827     <p>By providing both <code>_:track1</code> and <code>_:track2</code> as object values of the playlist
   828       along with an RDF Collection containing the ordered values, the data may be queried via a simple
   829       query using the playlist subject, or as an ordered collection.</p>
   830   </div></div>
   831 </section>
   833 <section class="informative" id="value-typing">
   834   <h3><span class="secno">3.3 </span>Value Typing</h3><p><em>This section is non-normative.</em></p>
   835   <p>In microdata, all values are strings. In RDF, values may be resources
   836    or may be typed with an appropriate datatype.</p>
   837   <p> In some cases, the type of a microdata value can be determined from the
   838    element on which it is specified. In particular:</p>
   839   <ul>
   840     <li>URL property elements provide URLs</li>
   841     <li><code>time</code> element provides dates and times</li>
   842   </ul>
   843   <div class="issue"><div class="issue-title"><span>Issue</span></div><p class="">Using information about the content of the document where the microdata
   844    is marked up <em>might</em> be a violation of the spirit of the microdata specification, though it does not explicitly say in
   845    normative text that consumers cannot use other information from the HTML DOM to interpret microdata.</p></div>
   847   <p>Additionally, one possible use of a <a href="#dfn-registry" class="internalDFN">registry</a> would allow vocabularies to be marked with datatype information,
   848     so that a <code>dc:time</code> value, for example, would be understood to represent a literal with datatype
   849     <code>xsd:date</code>. This could be done by adding information for each property in the vocabulary requiring
   850     special treatment.</p>
   851   <p>This might be represented using a syntax such as the following:</p>
   852   <div class="example"><div class="example-title"><span>Example 12</span></div><pre class="example">{
   853  "http://schema.org/": {
   854    "propertyURI": "vocabulary",
   855    "multipleValues": "unordered"<span class="diff">,
   856    "properties": {
   857      "dateCreated": {"datatype": "http://www.w3.org/2001/XMLSchema#date"}
   858    }</span>
   859  }
   860 }</pre></div>
   861   <p>The <code>datatype</code> identifies a URI to be used in constructing a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a>.</p>
   863   <p>In most cases, the relevant datatype for a value can be derived from
   864     knowledge of what property the value is for and the syntax of the value
   865     itself. Thus, values can be given datatypes in a post-processing step
   866     after the mapping of microdata to RDF described by this specification.
   867     However, where there is information in the HTML markup, such as knowledge
   868     of what element was used to mark up the value, which can help with
   869     determining its datatype, that information is used by this specification.</p>
   870   <p>This concept is not explored further at this time, but could be developed further in
   871     a future revision of this document.</p>
   873   <div class="note"><div class="note-title"><span>Note</span></div><p class="">If property URI generation was fixed to <code>vocabulary</code>, multiple values always
   874     generated both <code>unordered</code> and <code>ordered</code> representations, and there were <code>datatype</code>
   875     support, the <a href="#dfn-registry" class="internalDFN">registry</a> could be reduced to a simple list of URLs without any further structure necessary.</p></div>
   876 </section>
   877 </section>
   879 <section id="vocabulary-expansion">
   880   <!--OddPage--><h2 id="vocab_expansion"><span class="secno">4. </span>Vocabulary Expansion</h2>
   881   <p>Microdata requires that all values of <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a> come from the same vocabulary. This
   882     is required as <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a> values are resolved relative to that vocabulary. However,
   883     it is often useful to define an <a href="#dfn-item" class="internalDFN">item</a> to have types from multiple different vocabularies.</p>
   884   <p>Vocabulary expansion uses simple rules to generate additional triples based on 
   885     rules and property relationships described in the <a href="#dfn-registry" class="internalDFN">registry</a>.
   886     Within the <a href="#dfn-registry" class="internalDFN">registry</a>, a property definition may have either <code>equivalentProperty</code>
   887     or <code>subPropertyOf</code> keys having a IRI value (or array of IRI values)
   888     of the associated property. Such an
   889     entry causes the processor to generate triples associating the source
   890     property IRI with the target property IRI using either
   891     <code>http://www.w3.org/2000/01/rdf-schema#subPropertyOf</code> or
   892     <code>http://www.w3.org/2002/07/owl#equivalentProperty</code> predicates.</p>
   893    <p>For example, the <a href="#dfn-registry" class="internalDFN">registry</a> definition for the <em>additionalType</em> property
   894     within schema.org, defines <em>additionalType</em> to have an <a>rdfs:subPropertyOf</a>
   895     relationship with <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</code>.</p>
   897 <div class="example"><div class="example-title"><span>Example 13</span></div><pre class="example">{
   898   "http://schema.org/": {
   899     "properties": {
   900       <span class="diff">"additionalType": {"subPropertyOf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"}</span>
   901     }
   902 }
   904 &lt;div itemscope itemtype="http://schema.org/Person"&gt;
   905   &lt;link itemprop="additionalType" href="http://xmlns.com/foaf/0.1/Person"/&gt;
   906   &lt;a itemprop="email http://xmlns.com/foaf/0.1/mbox" href="mailto:mail@gmail.com"&gt;
   907     mail@gmail.com
   908   &lt;/a&gt;
   909 &lt;/div&gt;</pre></div>
   911   <p>The previous example, indicates a <a href="#dfn-registry" class="internalDFN">registry</a> rule, which causes the processor to emit
   912     an extra triple when first seeing the <code>additionalProperty</code> <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>:</p>
   914 <div class="example"><div class="example-title"><span>Example 14</span></div><pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .
   915 @prefix md: &lt;http://www.w3.org/ns/md#&gt; .
   916 @prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
   917 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
   918 @prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt; .
   919 @prefix schema: &lt;http://schema.org/&gt; .
   921 &lt;&gt; md:item (
   922   [ a schema:Person;
   923     schema:additionalType foaf:Person;
   924     schema:email &lt;mailto:mail@gmail.com&gt;;
   925     foaf:mbox &lt;mailto:mail@gmail.com&gt;]);
   926   rdfa:usesVocabulary schema: .
   928 schema:additionalType rdfs:subPropertyOf rdf:type .</pre></div>
   930   <p>After performing vocabulary expansion, an additional <code>rdf:type</code> triple is generated:</p>
   932 <div class="example"><div class="example-title"><span>Example 15</span></div><pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .
   933 @prefix md: &lt;http://www.w3.org/ns/md#&gt; .
   934 @prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
   935 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
   936 @prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt; .
   937 @prefix schema: &lt;http://schema.org/&gt; .
   939 &lt;&gt; md:item (
   940   [ a schema:Person, foaf:Person;
   941     schema:additionalType foaf:Person;
   942     schema:email &lt;mailto:mail@gmail.com&gt;;
   943     foaf:mbox &lt;mailto:mail@gmail.com&gt;]);
   944   rdfa:usesVocabulary schema: .
   946 schema:additionalType rdfs:subPropertyOf rdf:type .</pre></div>
   948 <section id="vocabulary-entailment">
   949   <h3><span class="secno">4.1 </span>Vocabulary Entailment</h3>
   950   <p>Formally, and for the purpose of vocabulary processing, microdata uses a very
   951     restricted subset of the OWL2 vocabulary and is based on the RDF-Based Semantics of OWL2 [<cite><a class="bibref" href="#bib-OWL2-RDF-BASED-SEMANTICS">OWL2-RDF-BASED-SEMANTICS</a></cite>].
   952     Vocabulary Entailment uses the following terms: </p>
   953   <ul>
   954     <li><code>rdfs:subPropertyOf</code></li>
   955     <li><code>owl:equivalentProperty</code>
   956     </li>
   957   </ul>
   958   <p>Vocabulary Entailment considers only the entailment on individuals
   959     (i.e., not on the relationships that can be deduced on the
   960     properties or the classes themselves.)
   961   </p>
   962   <div class="note"><div class="note-title"><span>Note</span></div><p class="">While the formal definition of the Entailment
   963     refers to the general OWL 2 Semantics, practical implementations may
   964     rely on a subset of the OWL 2 RL Profile’s entailment expressed in
   965     rules
   966     (<cite><a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/#Reasoning_in_OWL_2_RL_and_RDF_Graphs_using_Rules">
   967       section 4.3</a></cite>
   968     of [<cite><a class="bibref" href="#bib-OWL2-PROFILES">OWL2-PROFILES</a></cite>]). The
   969     relevant rules are, using the rule identifications in
   970     <cite><a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/#Reasoning_in_OWL_2_RL_and_RDF_Graphs_using_Rules">
   971       section 4.3</a></cite>
   972     of [<cite><a class="bibref" href="#bib-OWL2-PROFILES">OWL2-PROFILES</a></cite>]): <code>prp-spo1</code>, <code>prp-eqp1</code>, and
   973     <code>prp-eqp2</code>.</p></div>
   975   <p>[<cite><a class="bibref" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] implements a more complete form of vocabulary entailement, 
   976     including retrieving the vocabulary URI to find additional class and property expansion definitions, as
   977     described in <cite><a href="http://www.w3.org/TR/rdfa-syntax/#s_vocab_entailment">RDFa Vocabulary Entailment</a></cite>.
   978     Microdata implementations <em class="rfc2119" title="may">may</em> use RDFa Vocabulary Entailment as an alternative to implementing
   979     a separate entailment algorithm. To allow [<cite><a class="bibref" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] processors to be used for microdata vocabulary expansion, microdata acts as if there is an implicit <code>@vocab</code> RDFa attribute set to a detected vocabulary by emitting
   980     a triple using the <code>rdfa:usesVocabulary</code> predicate.</p>
   983   <div class="note"><div class="note-title"><span>Note</span></div><p class="">The entailment described in this section is the <em>minimum</em>
   984     useful level for microdata. Processors may, of course, choose to follow
   985     more powerful entailment regimes, e.g., include full RDFS [<cite><a class="bibref" href="#bib-RDF-MT">RDF-MT</a></cite>]
   986     or OWL2 [<cite><a class="bibref" href="#bib-OWL2-OVERVIEW">OWL2-OVERVIEW</a></cite>] entailments. Using those entailments
   987     applications may perform datatype validation by checking <code>rdfs:range</code>
   988     of a property, or use the advanced facilities offered by, e.g., OWL2’s
   989     property chains to interlink vocabularies further.</p></div>
   991 </section>
   993 <section id="vocabulary-expansion-control-of-microdata-processors">
   994   <h3><span class="secno">4.2 </span>Vocabulary Expansion Control of Microdata Processors</h3>
   995   <p>Conforming processors <em class="rfc2119" title="must">must</em> perform the basic vocabulary expansion.</p>
   996   <p>If vocabulary expansion is performed by the microdata processor using [<cite><a class="bibref" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] vocabulary expansion, and the
   997     <code>vocab_expansion</code> option is passed to the microdata processor,
   998     the full [<cite><a class="bibref" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>] expansion <em class="rfc2119" title="must">must</em> also be performed.</p>
   999 </section>
  1000 </section>
  1002 <section id="algorithm">
  1003   <!--OddPage--><h2><span class="secno">5. </span>Algorithm</h2>
  1004   <p>
  1005     Transformation of Microdata to RDF makes use of general processing rules described in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]
  1006     for the treatment of <a href="#dfn-item" class="internalDFN">item</a>s.
  1007   </p>
  1008   <section id="algorithm-terms">
  1009     <h3><span class="secno">5.1 </span>Algorithm Terms</h3>
  1010     <dl>
  1011       <dt><dfn id="dfn-absolute-url">absolute URL</dfn></dt><dd>
  1012         The term <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/urls.html#absolute-url">absolute URL</a></cite>
  1013         is defined in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>].
  1014       </dd>
  1015       <dt><dfn id="dfn-blank-node">blank node</dfn></dt><dd>
  1016         A blank node is a node in a graph that is neither a <a href="#dfn-uri-reference" class="internalDFN">URI reference</a> nor a <a href="#dfn-literal" class="internalDFN">literal</a>.
  1017         <a>Item</a>s without a <a href="#dfn-global-identifier" class="internalDFN">global identifier</a> have a blank node allocated to them.
  1018         (See [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
  1019       </dd>
  1020       <dt><dfn id="dfn-document-base">document base</dfn></dt><dd>
  1021         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
  1022         [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>].
  1023       </dd>
  1024       <dt><dfn id="dfn-evaluation-context">evaluation context</dfn></dt><dd>
  1025         A data structure including the following elements:
  1026         <dl>
  1027           <dt><dfn id="dfn-memory">memory</dfn></dt><dd>
  1028             a mapping of items to subjects, initially empty;
  1029           </dd>
  1030           <dt><dfn id="dfn-current-name">current name</dfn></dt><dd>
  1031             an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a> for the in-scope <a href="#dfn-name" class="internalDFN">name</a>, used for generating URIs
  1032             for properties of items without an <a href="#dfn-item-type" class="internalDFN">item type</a>;
  1033             <div class="note"><div class="note-title"><span>Note</span></div><div class="">
  1034               <a href="#dfn-current-name" class="internalDFN">current name</a> is required for the <code>contextual</code> property URI generation
  1035               scheme. Without this scheme, this evaluation context component would not be required.
  1036             </div></div>
  1037           </dd>
  1038           <dt><dfn id="dfn-current-type">current type</dfn></dt><dd>
  1039             an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a> for the <em>current type</em>, used when an <a href="#dfn-item" class="internalDFN">item</a> does not
  1040             contain an <a href="#dfn-item-type" class="internalDFN">item type</a>;
  1041           </dd>
  1042           <dt><dfn id="dfn-current-vocabulary">current vocabulary</dfn></dt><dd>
  1043             an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a> for the <em>current vocabulary</em>, from the <a href="#dfn-registry" class="internalDFN">registry</a>.
  1044           </dd>
  1045         </dl>
  1046       </dd>
  1047       <dt><dfn id="dfn-item">item</dfn></dt><dd>
  1048          An <a href="#dfn-item" class="internalDFN">item</a> is described by an element containing an <a class="aref internalDFN" href="#dfn-itemscope">itemscope</a> attribute. The list
  1049          of top-level microdata items may be retrieved using the
  1050          <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite>
  1051          <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-document-getitems">document.getItems</a></cite></code>
  1052          method.
  1053       </dd>
  1054       <dt><dfn id="dfn-item-properties">item properties</dfn></dt><dd>
  1055         The mechanism for finding the <a title="item properties" href="#dfn-item-properties" class="internalDFN">properties of an item</a> The list
  1056          of item properties items may be retrieved using the
  1057          <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite>
  1058          <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-properties">element.properties</a></cite></code>
  1059          attribute.
  1060       </dd>
  1061       <dt><dfn id="dfn-fragment-escape">fragment-escape</dfn></dt><dd>
  1062         The term <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/urls.html#fragment-escaped">fragment-escape</a></cite>
  1063         is defined in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>]. This involves transforming elements added to URLs to ensure that the result
  1064         remains a valid URL. The following characters are subject to percent escaping:
  1065         <ul>
  1066           <li>U+0022 QUOTATION MARK character (")</li>
  1067           <li>U+0023 NUMBER SIGN character (#)</li>
  1068           <li>U+0025 PERCENT SIGN character (%)</li>
  1069           <li>U+003C LESS-THAN SIGN character (&lt;)</li>
  1070           <li>U+003E GREATER-THAN SIGN character (&gt;)</li>
  1071           <li>U+005B LEFT SQUARE BRACKET character ([)</li>
  1072           <li>U+005C REVERSE SOLIDUS character (\)</li>
  1073           <li>U+005D RIGHT SQUARE BRACKET character (])</li>
  1074           <li>U+005E CIRCUMFLEX ACCENT character (^)</li>
  1075           <li>U+007B LEFT CURLY BRACKET character ({)</li>
  1076           <li>U+007C VERTICAL LINE character (|)</li>
  1077           <li>U+007D RIGHT CURLY BRACKET character (})</li>
  1078         </ul>
  1079       </dd>
  1080       <dt><dfn id="dfn-global-identifier">global identifier</dfn></dt><dd>
  1081         The value of an <a href="#dfn-item" class="internalDFN">item</a>'s <a href="#dfn-itemid" class="internalDFN">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
  1082         [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
  1083       </dd>
  1084       <dt><dfn id="dfn-literal">literal</dfn></dt><dd>
  1085         Literals are values such as strings and dates, including <dfn id="dfn-typed-literal">typed literal</dfn>s and
  1086         <dfn id="dfn-plain-literal">plain literal</dfn>s.
  1087         (See [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
  1088       </dd>
  1089       <dt><dfn id="dfn-property">property</dfn></dt><dd>
  1090         Each <a href="#dfn-name" class="internalDFN">name</a> identifies a <a href="#dfn-property" class="internalDFN">property</a> of an <a href="#dfn-item" class="internalDFN">item</a>.
  1091         An <a href="#dfn-item" class="internalDFN">item</a> may have multiple elements sharing the same <a href="#dfn-name" class="internalDFN">name</a>, creating
  1092         a multi-valued <a href="#dfn-property" class="internalDFN">property</a>.
  1093        </dd>
  1094      <dt><dfn id="dfn-property-names">property names</dfn></dt><dd>
  1095         The tokens of an element's <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a> attribute. Each token is a <a href="#dfn-name" class="internalDFN">name</a>.
  1096         (See <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#property-names">Names: the
  1097         itemprop attribute</a></cite> in [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>]).
  1098       </dd>
  1099       <dt><dfn id="dfn-property-value">property value</dfn></dt><dd>
  1100         The <a href="#dfn-property-value" class="internalDFN">property value</a> of a name-value pair added by an element with an <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>
  1101         attribute depends on the element.
  1102         <dl>
  1103           <dt>If the element has no <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a> attribute</dt>
  1104           <dd>The value is null and no triple should be generated.</dd>
  1105           <dt>If the element creates an <a href="#dfn-item" class="internalDFN">item</a> (by having an <a class="aref internalDFN" href="#dfn-itemscope">itemscope</a> attribute)</dt>
  1106           <dd>
  1107             The value is the <a href="#dfn-uri-reference" class="internalDFN">URI reference</a> or <a href="#dfn-blank-node" class="internalDFN">blank node</a> returned from
  1108             <a href="#generate-the-triples">generate the triples</a> for that <a href="#dfn-item" class="internalDFN">item</a>.
  1109           </dd>
  1110           <dt>If the element is a URL property element (<code>a</code>, <code>area</code>, <code>audio</code>,
  1111             <code>embed</code>, <code>iframe</code>, <code>img</code>, <code>link</code>, <code>object</code>,
  1112             <code>source</code>, <code>track</code> or <code>video</code>)</dt>
  1113           <dd>
  1114             The value is a <a href="#dfn-uri-reference" class="internalDFN">URI reference</a> created from <code><cite>
  1115               <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemvalue">element.itemValue</a></cite></code>.
  1116               (See relevant attribute descriptions in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>]).
  1117           </dd>
  1118           <dt>If the element is a <code>time</code> element.</dt>
  1119           <dd>The value is a <a href="#dfn-literal" class="internalDFN">literal</a> made from <code><cite>
  1120             <a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemvalue">element.itemValue</a></cite></code>.
  1121             <dl>
  1122               <dt>
  1123                 If the value is a
  1124                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-date-string">
  1125                   valid date string
  1126                 </a></cite>
  1127                 having the lexical form of
  1128                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#date">xsd:date</a></cite> [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1129               </dt>
  1130               <dd>
  1131                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1132                 <code>http://www.w3.org/2001/XMLSchema#date</code>.
  1133               </dd>
  1134               <dt>
  1135                 If the value is a
  1136                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-time-string">
  1137                   valid time string
  1138                 </a></cite>
  1139                 having the lexical form of
  1140                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#time">xsd:time</a></cite> [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1141               </dt>
  1142               <dd>
  1143                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1144                 <code>http://www.w3.org/2001/XMLSchema#time</code>.
  1145               </dd>
  1146               <dt>
  1147                 If the value is a
  1148                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-local-date-and-time-string">
  1149                   valid local date and time string
  1150                 </a></cite>
  1151                 or
  1152                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-global-date-and-time-string">
  1153                   valid global date and time string
  1154                 </a></cite>
  1155                 having the lexical form of
  1156                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#dateTime">xsd:dateTime</a></cite> [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1157               </dt>
  1158               <dd>
  1159                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1160                <code>http://www.w3.org/2001/XMLSchema#dateTime</code>.
  1161               </dd>
  1162               <dt>
  1163                 If the value is a
  1164                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-month-string">
  1165                   valid month string
  1166                 </a></cite>
  1167                 having the lexical form of
  1168                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#gYearMonth">xsd:gYearMonth</a></cite> [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1169               </dt>
  1170               <dd>
  1171                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1172                <code>http://www.w3.org/2001/XMLSchema#gYearMonth</code>.
  1173               </dd>
  1174               <dt>
  1175                 If the value is a
  1176                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/common-microsyntaxes.html#valid-non-negative-integer">
  1177                   valid non-negative integer
  1178                 </a></cite>
  1179                 having the lexical form of
  1180                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#gYear">xsd:gYear</a></cite> [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1181               </dt>
  1182               <dd>
  1183                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1184                <code>http://www.w3.org/2001/XMLSchema#gYear</code>.
  1185               </dd>
  1186               <dt>
  1187                 If the value has the lexical form of
  1188                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#duration">xsd:duration</a></cite>
  1189                 [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].
  1190                 <!--
  1191                 If the value is a
  1192                 <cite><a href="http://dev.w3.org/html5/spec/Overview.html#valid-duration-string">
  1193                   valid duration string
  1194                 </a></cite>
  1195                 having the lexical form of
  1196                 <cite><a href="http://www.w3.org/TR/xmlschema-2/#duration">xsd:duration</a></cite> [[!RDF-SCHEMA]].
  1197                 -->
  1198               </dt>
  1199               <dd>
  1200                 The value is a <a href="#dfn-typed-literal" class="internalDFN">typed literal</a> composed of the value and
  1201                 <code>http://www.w3.org/2001/XMLSchema#duration</code>.
  1202                 <div class="note"><div class="note-title"><span>Note</span></div><p class="">The referenced version of [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>] does not include a <em>duration</em> data type,
  1203                   but it is in the Editor's Draft and is expected to be included in a
  1204                   forthcoming update to the Working Draft</p></div>
  1205               </dd>
  1206               <dt>Otherwise</dt>
  1207               <dd>
  1208                 The value is a <a href="#dfn-plain-literal" class="internalDFN">plain literal</a> created from the value with language information set from the
  1209                 <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/elements.html#language">language</a></cite>
  1210                 of the property element.
  1211                 <div class="note"><div class="note-title"><span>Note</span></div><p class="">The HTML
  1212                   <em>valid yearless date string</em>
  1213                   is similar to
  1214                   <cite><a href="http://www.w3.org/TR/xmlschema-2/#gMonthDay">xsd:gMonthDay</a></cite>,
  1215                   but the lexical forms differ, so it is not included in this conversion.</p></div>
  1216               </dd>
  1217             </dl>
  1218             <p>See
  1219               <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/rendering.html#the-time-element-0">
  1220                 The <code>time</code> element
  1221               </a></cite>
  1222               in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>].</p>
  1223           </dd>
  1224           <dt>Otherwise</dt>
  1225           <dd>The value is a <a href="#dfn-plain-literal" class="internalDFN">plain literal</a> created from the value with language information set from the
  1226             <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/elements.html#language">language</a></cite> of the property element.
  1227             <p>See
  1228               <cite><a href="http://www.w3.org/TR/2011/WD-html5-20110525/elements.html#the-lang-and-xml:lang-attributes">
  1229                 The <code>lang</code> and <code>xml:lang</code> attributes
  1230               </a></cite>
  1231               in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>] for determining the language of a node.</p>
  1232           </dd>
  1233         </dl>
  1234       </dd>
  1235       <dt><dfn id="dfn-top-level-item">top-level item</dfn></dt><dd>
  1236         An <a href="#dfn-item" class="internalDFN">item</a> which does not contain an <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a> attribute.
  1237         Available through the <cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#microdata-dom-api">Microdata DOM API</a></cite> as
  1238         <code>document.getItems</code>.
  1239         (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" href="#bib-MICRODATA">MICRODATA</a></cite>]).
  1240       </dd>
  1241       <dt><dfn id="dfn-uri-reference">URI reference</dfn></dt><dd>
  1242         URI references are suitable to be used in <em>subject</em>, <em>predicate</em> or <em>object</em> positions
  1243         within an RDF triple, as opposed to a <a href="#dfn-literal" class="internalDFN">literal</a> value that may contain a string representation of a
  1244         URI. (See [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]).
  1245         <div class="issue"><div class="issue-title"><span>Issue</span></div><div class="">
  1246           <p>The HTML5/microdata content model for <code>@href</code>, <code>@src</code>,
  1247             <code>@data</code>, <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a> and <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a> and <a class="aref internalDFN" href="#dfn-itemid">itemid</a> is that of
  1248             a URL, not a URI or IRI.</p>
  1249           <p>A proposed mechanism for specifying the range of <a href="#dfn-property-value" class="internalDFN">property value</a>s to be URI reference or IRI could
  1250             allow these to be specified as subject or object using a <code>@content</code> attribute.</p>
  1251         </div></div>
  1252       </dd>
  1253       <dt><dfn id="dfn-vocabulary">vocabulary</dfn></dt><dd>
  1254         A vocabulary is a collection of URIs, suitable for use as an <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a> or <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>
  1255         value, that share a common <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a>. That prefix is the vocabulary URI. A vocabulary URI is not
  1256         allowed to be a prefix of another vocabulary URI.
  1257         <div class="note"><div class="note-title"><span>Note</span></div><div class="">
  1258           This definition differs from the language in the HTML spec and is just for the purpose of this
  1259           document. In HTML, a vocabulary is a specification, and doesn't have a URI. In our view, if one
  1260           specification defines ten <a class="aref internalDFN" href="#dfn-itemtype">itemtype</a>s, then these could be treated as one vocabulary or as ten
  1261           distinct vocabularies; it is entirely up to the vocabulary creator.
  1262         </div></div>
  1263       </dd>
  1264     </dl>
  1265   </section>
  1267   <section id="rdf-conversion-algorithm">
  1268     <h3><span class="secno">5.2 </span>RDF Conversion Algorithm</h3>
  1269     <p>A HTML document containing microdata <em class="rfc2119" title="may">may</em> be converted to any other RDF-compatible document
  1270     format using the algorithm specified in this section.</p>
  1271     <p>A conforming microdata processor implementing RDF conversion <em class="rfc2119" title="must">must</em> implement a
  1272       processing algorithm that results in the equivalent triples to those that the following
  1273       algorithm generates:</p>
  1275     <p>Set <em>item list</em> to an empty list.</p>
  1277     <ol class="algorithm">
  1278       <li>For each element that is also a <a href="#dfn-top-level-item" class="internalDFN">top-level item</a> run the following algorithm:
  1279         <ol class="algorithm">
  1280           <li>
  1281             <a href="#generate-the-triples">Generate the triples</a> for an item <em>item</em>, using the
  1282             <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a>.
  1283             Let <em>result</em> be the (<a href="#dfn-uri-reference" class="internalDFN">URI reference</a> or <a href="#dfn-blank-node" class="internalDFN">blank node</a>) subject returned.
  1284           </li>
  1285           <li>
  1286             Append <em>result</em> to <em>item list</em>.
  1287           </li>
  1288         </ol>
  1289       </li>
  1290       <li>
  1291         <a href="#generate-collection">Generate an RDF Collection</a> <em>list</em> from the ordered list of values.
  1292         Set <em>value</em> to the value returned from <a href="#generate-collection">generate an RDF
  1293         Collection</a>.
  1294       </li>
  1295       <li>
  1296         Generate the following triple:
  1297         <dl class="triple">
  1298           <dt>subject</dt>
  1299           <dd><a href="#dfn-document-base" class="internalDFN">document base</a></dd>
  1300           <dt>predicate</dt>
  1301           <dd><code>http://www.w3.org/ns/md#item</code></dd>
  1302           <dt>object</dt>
  1303           <dd><em>value</em></dd>
  1304         </dl>
  1305       </li>
  1306       <li>
  1307         Perform <a href="#vocabulary-entailment">Vocabulary Entailment</a>.</li>
  1308     </ol>
  1309   </section>
  1311   <section id="generate-the-triples">
  1312     <h3><span class="secno">5.3 </span>Generate the triples</h3>
  1313     <p>
  1314       When the user agent is to Generate triples for an <a href="#dfn-item" class="internalDFN">item</a> <em>item</em>, given
  1315       <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a>, it must run the following steps:
  1316     </p>
  1317     <div class="note"><div class="note-title"><span>Note</span></div><p class="">
  1318       This algorithm has undergone substantial change from the original microdata specification [<cite><a class="bibref" href="#bib-MICRODATA">MICRODATA</a></cite>].
  1319     </p></div>
  1320     <ol class="algorithm">
  1321       <li>
  1322         If there is an entry for <em>item</em> in <a href="#dfn-memory" class="internalDFN">memory</a>, then let <em>subject</em> be the subject of
  1323         that entry. Otherwise, if <em>item</em> has a <a href="#dfn-global-identifier" class="internalDFN">global identifier</a> and that
  1324         <a href="#dfn-global-identifier" class="internalDFN">global identifier</a> is an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>, let <em>subject</em> be that
  1325         <a href="#dfn-global-identifier" class="internalDFN">global identifier</a>. Otherwise, let <em>subject</em> be a new <a href="#dfn-blank-node" class="internalDFN">blank node</a>.
  1326       </li>
  1327       <li>Add a mapping from <em>item</em> to <em>subject</em> in <a href="#dfn-memory" class="internalDFN">memory</a></li>
  1328       <li>
  1329         For each <em>type</em> returned from
  1330         <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
  1331         of the element defining the <a href="#dfn-item" class="internalDFN">item</a>.
  1332         <ol class="algorithm">
  1333           <li>If <em>type</em> is an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>, generate the following triple:
  1334             <dl class="triple">
  1335               <dt>subject</dt>
  1336               <dd><em>subject</em></dd>
  1337               <dt>predicate</dt>
  1338               <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</code></dd>
  1339               <dt>object</dt>
  1340               <dd><em>type</em> (as a <a href="#dfn-uri-reference" class="internalDFN">URI reference</a>)</dd>
  1341             </dl>
  1342           </li>
  1343         </ol>
  1344       </li>
  1345       <li>
  1346         Set <em>type</em> to the first value returned from
  1347         <code><cite><a href="http://www.w3.org/TR/2011/WD-microdata-20110525/#dom-itemtype">element.itemType</a></cite></code>
  1348         of the element defining the <a href="#dfn-item" class="internalDFN">item</a>.
  1349       </li>
  1350       <li>If <em>type</em> is an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>, set <a href="#dfn-current-name" class="internalDFN">current name</a> in
  1351         <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a> to null.</li>
  1352       <li>
  1353         Otherwise, set <em>type</em> to <a href="#dfn-current-type" class="internalDFN">current type</a> from
  1354         <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a> if not empty.
  1355       </li>
  1356       <li>If the <a href="#dfn-registry" class="internalDFN">registry</a> contains a <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> that is a
  1357         character for character match of <em>type</em> up to the length of the 
  1358         <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a>, set <em>vocab</em> as that <a href="#dfn-uri-prefix" class="internalDFN">URI prefix</a> and 
  1359         generate the following triple:
  1360         <dl class="triple">
  1361           <dt>subject</dt>
  1362           <dd><a href="#dfn-document-base" class="internalDFN">document base</a></dd>
  1363           <dt>predicate</dt>
  1364           <dd><code>http://www.w3.org/ns/rdfa#usesVocabulary</code></dd>
  1365           <dt>object</dt>
  1366           <dd><em>vocab</em> (as a <a href="#dfn-uri-reference" class="internalDFN">URI reference</a>)</dd>
  1367         </dl>
  1368       </li>
  1369       <li>Otherwise, if type is not empty, construct <em>vocab</em> by removing everything following the last
  1370         SOLIDUS U+002F ("/") or NUMBER SIGN U+0023 ("#") from the <em>path</em> component of <em>type</em>.</li>
  1371       <li>Update <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a> setting <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a> to <em>vocab</em>.</li> 
  1372       <li>
  1373         Set <em>property list</em> to an empty array mapping properties to one or more
  1374         <em>value</em>s as established below.
  1375       </li>
  1376       <li>
  1377         For each element <em>element</em> that has one or more <a href="#dfn-property-names" class="internalDFN">property names</a> and is one of the
  1378         <a title="item properties" href="#dfn-item-properties" class="internalDFN">properties of the item</a> <em>item</em>, in the order those elements
  1379         are given by the algorithm that returns the <a title="item properties" href="#dfn-item-properties" class="internalDFN">properties of the item</a>,
  1380         run the following substep:
  1381         <ol class="algorithm">
  1382           <li>
  1383             For each <em>name</em> in the element's <a href="#dfn-property-names" class="internalDFN">property names</a>, run the following substeps:
  1384             <ol class="algorithm">
  1385               <li>
  1386                 Let <em>context</em> be a copy of <a href="#dfn-evaluation-context" class="internalDFN">evaluation context</a> with <a href="#dfn-current-type" class="internalDFN">current type</a> set
  1387                 to <em>type</em>.
  1388               </li>
  1389               <li>
  1390                 Let <em>predicate</em> be the result of <a href="#generate-predicate-uri">generate predicate URI</a>
  1391                 using <em>context</em> and <em>name</em>.
  1392                  Update <em>context</em> by setting <a href="#dfn-current-name" class="internalDFN">current name</a> to <em>predicate</em>.
  1393               </li>
  1394               <li>
  1395                 Let <em>value</em> be the <a href="#dfn-property-value" class="internalDFN">property value</a> of <em>element</em>.
  1396               </li>
  1397               <li>
  1398                 If <em>value</em> is an <a href="#dfn-item" class="internalDFN">item</a>, then <a href="#generate-the-triples">generate the
  1399                 triples</a> for <em>value</em> using <em>context</em>. Replace <em>value</em> by the subject returned
  1400                 from those steps.
  1401               </li>
  1402               <li>
  1403                 Add <em>value</em> to <em>property list</em> for <em>predicate</em>.
  1404               </li>
  1405             </ol>
  1406           </li>
  1407         </ol>
  1408       </li>
  1409       <li>
  1410         For each <em>predicate</em> in <em>property list</em>:
  1411         <ol class="algorithm">
  1412           <li><a href="#generate-property-values">Generate property values</a> <em>subject</em>, <em>predicate</em> and
  1413             the list of values associated with <em>predicate</em> from <em>property list</em> as <em>values</em>.
  1414           </li>
  1415         </ol>
  1416       </li>
  1417       <li>Return <em>subject</em></li>
  1418     </ol>
  1419   </section>
  1421   <section id="generate-predicate-uri">
  1422     <h3><span class="secno">5.4 </span>Generate Predicate URI</h3>
  1423     <p>Predicate URI generation makes use of <a href="#dfn-current-type" class="internalDFN">current type</a>,
  1424       <a href="#dfn-current-name" class="internalDFN">current name</a>, and <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a> from an <a href="#dfn-evaluation-context" class="internalDFN">evaluation
  1425       context</a> <em>context</em> along with <em>name</em>.</p>
  1427     <ol class="algorithm">
  1428       <li>If <em>name</em> is an <a href="#dfn-absolute-url" class="internalDFN">absolute URL</a>, return <em>name</em>
  1429         as a <a href="#dfn-uri-reference" class="internalDFN">URI reference</a>.</li>
  1430       <li>If <a href="#dfn-current-type" class="internalDFN">current type</a> from <em>context</em> is null,
  1431         there can be no <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a>. Return the <a href="#dfn-uri-reference" class="internalDFN">URI reference</a>
  1432         that is the <a href="#dfn-document-base" class="internalDFN">document base</a> with its <cite><a href="http://tools.ietf.org/html/rfc3986#section-3.5">fragment</a></cite>
  1433         set to the <a href="#dfn-fragment-escape" class="internalDFN">fragment-escape</a>d value of <em>name</em>.
  1434         <div class="note"><div class="note-title"><span>Note</span></div><div class="">
  1435           This rule is intended to allow for a the case where no type is set, and
  1436           therefore there is no vocabulary from which to extract rules. For
  1437           example, if there is a <a href="#dfn-document-base" class="internalDFN">document base</a> of
  1438           <code>http://example.org/doc</code> and an <a class="aref internalDFN" href="#dfn-itemprop">itemprop</a>
  1439           of 'title', a URI will be constructed to be
  1440           <code>http://example.org/doc#title</code>.
  1441         </div></div>
  1442       </li>
  1443       <li>Otherwise, if <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a> from <em>context</em>
  1444         is not null and <a href="#dfn-registry" class="internalDFN">registry</a> has an entry for <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a>
  1445         having a <a href="#dfn-propertyuri" class="internalDFN">propertyURI</a> entry that is not null, set that as
  1446         <em>scheme</em>. Otherwise, set <em>scheme</em> to
  1447         <code>vocabulary</code>.</li>
  1448       <li id="scheme-vocab">If <em>scheme</em> is <code>vocabulary</code>
  1449         set <em>expandedURI</em> to the <a href="#dfn-uri-reference" class="internalDFN">URI reference</a> constructed by
  1450         appending the <a href="#dfn-fragment-escape" class="internalDFN">fragment-escape</a>d value of <em>name</em> to <a href="#dfn-current-vocabulary" class="internalDFN">current
  1451         vocabulary</a>, separated by a U+0023 NUMBER SIGN character (#) unless the
  1452         <a href="#dfn-current-vocabulary" class="internalDFN">current vocabulary</a> ends with either a U+0023 NUMBER SIGN character
  1453         (#) or SOLIDUS U+002F (/).</li>
  1454       <li id="scheme-context">Otherwise, if <em>scheme</em> is
  1455         <code>contextual</code>, set <em>expandedURI</em> to the <a href="#dfn-uri-reference" class="internalDFN">URI
  1456         reference</a> constructed as follows:
  1457         <ol class="algorithm">
  1458           <li>Let <em>s</em> be <a href="#dfn-current-name" class="internalDFN">current name</a> from <em>context</em>.</li>
  1459           <li>If <code>http://www.w3.org/ns/md?type=</code>
  1460             is a prefix of <em>s</em>, return the concatenation of <em>s</em>, a
  1461             U+002E FULL STOP character (.) and the <a href="#dfn-fragment-escape" class="internalDFN">fragment-escape</a>d value
  1462             of <em>name</em>.</li>
  1463           <li>Otherwise, return the concatenation of
  1464             <code>http://www.w3.org/ns/md?type=</code>, the
  1465             <a href="#dfn-fragment-escape" class="internalDFN">fragment-escape</a>d value of <a href="#dfn-current-type" class="internalDFN">current type</a>, the string
  1466             <code>&amp;prop=</code>, and the <a href="#dfn-fragment-escape" class="internalDFN">fragment-escape</a>d value of
  1467             <em>name</em>. </li>
  1468         </ol>
  1469       </li>
  1470       <li>If the <a href="#dfn-registry" class="internalDFN">registry</a> entry for <a href="#dfn-propertyuri" class="internalDFN">propertyURI</a>
  1471         has an <code>equivalentProperty</code> key,
  1472         generate the following triple using the
  1473         <em>value</em> of that key:
  1474         <dl class="triple">
  1475           <dt>subject</dt>
  1476           <dd><em>expandedURI</em></dd>
  1477           <dt>predicate</dt>
  1478           <dd><code>http://www.w3.org/2002/07/owl#equivalentProperty</code></dd>
  1479           <dt>object</dt>
  1480           <dd><em>value</em></dd>
  1481         </dl>
  1482         <p>If the value is an array, generate a triple for each value of that array.</p>
  1483       </li>
  1484       <li>If the <a href="#dfn-registry" class="internalDFN">registry</a> entry for <a href="#dfn-propertyuri" class="internalDFN">propertyURI</a>
  1485         has an <code>subPropertyOf</code> key, generate the following triple using the
  1486         <em>value</em> of that key:
  1487         <dl class="triple">
  1488           <dt>subject</dt>
  1489           <dd><em>expandedURI</em></dd>
  1490           <dt>predicate</dt>
  1491           <dd><code>http://www.w3.org/2000/01/rdf-schema#subPropertyOf</code></dd>
  1492           <dt>object</dt>
  1493           <dd><em>value</em></dd>
  1494         </dl>
  1495         <p>If the value is an array, generate a triple for each value of that array.</p>
  1496       </li>
  1497       <li>Return <em>expandedURI</em>.</li>
  1498     </ol>
  1499   </section>
  1501   <section id="generate-property-values">
  1502     <h3><span class="secno">5.5 </span>Generate Property Values</h3>
  1503     <p>Property value serialization makes use of <em>subject</em>, <em>predicate</em> and <em>values</em>.</p>
  1505     <ol class="algorithm">
  1506       <li>If the <a href="#dfn-registry" class="internalDFN">registry</a> contains a URI prefix that is a character for character match of
  1507         <em>predicate</em> up to the length of the URI prefix, set <em>vocab</em> as that URI prefix.
  1508          Otherwise set <em>vocab</em> to null.</li>
  1509       <li>If <em>vocab</em> is not null
  1510         and <a href="#dfn-registry" class="internalDFN">registry</a> has an entry for <em>vocab</em> that is a JSON Object, let
  1511         <em>registry object</em> be that value. Otherwise set <em>registry object</em> to null.</li>
  1512       <li>If <em>registry object</em> is not null and <em>registry object</em> contains key
  1513         <a href="#dfn-properties" class="internalDFN"><code>properties</code></a>
  1514         which has a JSON Object value, let <em>properties</em> be that value. Otherwise, set <em>properties</em>
  1515         to null.</li>
  1516       <li>If <em>properties</em> is not null, and <em>properties</em> contains a key, which after
  1517         <a href="#generate-predicate-uri">Generate Predicate URI</a> expansion has a value which is a JSON Object, let
  1518         <em>property override</em> be that value. Otherwise, set <em>property override</em> to null.</li>
  1519       <li>If <em>property override</em> contains the key
  1520         <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a>, set that as <em>method</em>.</li>
  1521       <li>Otherwise, if <em>registry object</em> con  contains the key
  1522         <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a>, set that as <em>method</em>.</li>
  1523       <li>Otherwise, set <em>method</em> to <code>unordered</code>.</li>
  1524       <li id="values-unordered">If <em>method</em> is <code>unordered</code>,
  1525         for each <em>value</em> in <em>values</em>, generate the following triple:
  1526         <dl class="triple">
  1527           <dt>subject</dt>
  1528           <dd><em>subject</em></dd>
  1529           <dt>predicate</dt>
  1530           <dd><em>predicate</em></dd>
  1531           <dt>object</dt>
  1532           <dd><em>value</em></dd>
  1533         </dl>
  1534       </li>
  1535       <li id="values-list">Otherwise, if <em>method</em> is <code>list</code>:
  1536         <ol class="algorithm">
  1537           <li>Set <em>value</em> to the value returned from <a href="#generate-collection">generate an RDF
  1538             Collection</a>.
  1539           </li>
  1540           <li>
  1541             Generate the following triple:
  1542             <dl class="triple">
  1543               <dt>subject</dt>
  1544               <dd><em>subject</em></dd>
  1545               <dt>predicate</dt>
  1546               <dd><em>predicate</em></dd>
  1547               <dt>object</dt>
  1548               <dd><em>value</em></dd>
  1549             </dl>
  1550           </li>
  1551         </ol>
  1552       </li>
  1553     </ol>
  1554   </section>
  1556   <section id="generate-collection">
  1557     <h3><span class="secno">5.6 </span>Generate RDF Collection</h3>
  1558     <p>
  1559       An <dfn 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
  1560       [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>]). As the RDF data-model is that of an unordered graph, a linking method using properties
  1561       <code>rdf:first</code> and <code>rdf:next </code>is required to be able to specify a particular order.
  1562     </p>
  1563     <p>
  1564       In the microdata to RDF mapping, <a href="#dfn-rdf-collection" class="internalDFN">RDF Collection</a>s are used when an item has more than one value
  1565       associated with a given property to ensure that the original document order is maintained. The following
  1566       procedure should be used to generate triples when an <a href="#dfn-item" class="internalDFN">item</a> property has more than one value
  1567       (contained in <em>list</em>):
  1568     </p>
  1569     <ol class="algorithm">
  1570       <li>
  1571         Create a new array <em>array</em> containing a <a href="#dfn-blank-node" class="internalDFN">blank node</a> for every value in <em>list</em>.
  1572       </li>
  1573       <li>
  1574         For each pair of <em>bnode</em> from <em>array</em> and <em>value</em> from <em>list</em> the following
  1575         triple is generated:
  1576         <dl class="triple">
  1577           <dt>subject</dt>
  1578           <dd><em>bnode</em></dd>
  1579           <dt>predicate</dt>
  1580           <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#first</code></dd>
  1581           <dt>object</dt>
  1582           <dd><em>value</em></dd>
  1583         </dl>
  1584       </li>
  1585       <li>
  1586         For each <em>bnode</em> in <em>array</em> the following triple is generated:
  1587         <dl class="triple">
  1588           <dt>subject</dt>
  1589           <dd><em>bnode</em></dd>
  1590           <dt>predicate</dt>
  1591           <dd><code>http://www.w3.org/1999/02/22-rdf-syntax-ns#rest</code></dd>
  1592           <dt>object</dt>
  1593           <dd>
  1594             next <em>bnode</em> in <em>array</em> or, if that does not exist,
  1595             <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#nil</code>
  1596           </dd>
  1597         </dl>
  1598       </li>
  1599       <li>
  1600         Return the first <a href="#dfn-blank-node" class="internalDFN">blank node</a> from <em>array</em>.
  1601       </li>
  1602     </ol>
  1603   </section>
  1604 </section>
  1606 <section class="appendix informative" id="testing">
  1607   <!--OddPage--><h2><span class="secno">A. </span>Testing</h2><p><em>This section is non-normative.</em></p>
  1608   <p>A test suite [<cite><a class="bibref" href="#bib-MICRODATA-RDF-TESTS">MICRODATA-RDF-TESTS</a></cite>] under development to help processor developers verify
  1609     conformance to this specification.</p>
  1610 </section>
  1612 <section class="appendix informative" id="markup-examples">
  1613 <!--OddPage--><h2><span class="secno">B. </span>Markup Examples</h2><p><em>This section is non-normative.</em></p>
  1615 <p>The microdata example below expresses book information as an FRBR Work item.</p>
  1617 <div class="example"><div class="example-title"><span>Example 16</span></div><pre class="example">&lt;dl itemscope
  1618     itemtype="http://purl.org/vocab/frbr/core#Work"
  1619     itemid="http://books.example.com/works/45U8QJGZSQKDH8N"
  1620     lang="en"&gt;
  1621  &lt;dt&gt;Title&lt;/dt&gt;
  1622  &lt;dd&gt;&lt;cite itemprop="http://purl.org/dc/terms/title"&gt;Just a Geek&lt;/cite&gt;&lt;/dd&gt;
  1623  &lt;dt&gt;By&lt;/dt&gt;
  1624  &lt;dd&gt;&lt;span itemprop="http://purl.org/dc/terms/creator"&gt;Wil Wheaton&lt;/span&gt;&lt;/dd&gt;
  1625  &lt;dt&gt;Format&lt;/dt&gt;
  1626  &lt;dd itemprop="http://purl.org/vocab/frbr/core#realization"
  1627      itemscope
  1628      itemtype="http://purl.org/vocab/frbr/core#Expression"
  1629      itemid="http://books.example.com/products/9780596007683.BOOK"&gt;
  1630   &lt;link itemprop="http://purl.org/dc/terms/type" href="http://books.example.com/product-types/BOOK"&gt;
  1631   Print
  1632  &lt;/dd&gt;
  1633  &lt;dd itemprop="http://purl.org/vocab/frbr/core#realization"
  1634      itemscope
  1635      itemtype="http://purl.org/vocab/frbr/core#Expression"
  1636      itemid="http://books.example.com/products/9780596802189.EBOOK"&gt;
  1637   &lt;link itemprop="http://purl.org/dc/terms/type" href="http://books.example.com/product-types/EBOOK"&gt;
  1638   Ebook
  1639  &lt;/dd&gt;
  1640 &lt;/dl&gt;</pre></div>
  1642 <p>Assuming that <a href="#dfn-registry" class="internalDFN">registry</a> contains a an entry for <code>http://purl.org/vocab/frbr/core#</code>
  1643   with <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  1644   this is equivalent to the following Turtle:</p>
  1645 <div class="example"><div class="example-title"><span>Example 17</span></div><pre class="example">@prefix dc: &lt;http://purl.org/dc/terms/&gt; .
  1646 @prefix md: &lt;http://www.w3.org/ns/md#&gt; .
  1647 @prefix frbr: &lt;http://purl.org/vocab/frbr/core#&gt; .
  1648 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
  1650 &lt;&gt; md:item (&lt;http://books.example.com/works/45U8QJGZSQKDH8N&gt;) ;
  1651   rdfa:usesVocabulary frbr: .
  1653 &lt;http://books.example.com/works/45U8QJGZSQKDH8N&gt; a frbr:Work ;
  1654   dc:creator "Wil Wheaton"@en ;
  1655   dc:title "Just a Geek"@en ;
  1656   frbr:realization &lt;http://books.example.com/products/9780596007683.BOOK&gt;,
  1657     &lt;http://books.example.com/products/9780596802189.EBOOK&gt; .
  1659 &lt;http://books.example.com/products/9780596007683.BOOK&gt; a frbr:Expression ;
  1660   dc:type &lt;http://books.example.com/product-types/BOOK&gt; .
  1662 &lt;http://books.example.com/products/9780596802189.EBOOK&gt; a frbr:Expression ;
  1663   dc:type &lt;http://books.example.com/product-types/EBOOK&gt; .</pre></div>
  1665 <p>The following snippet of HTML has microdata for two people with the same address. This illustrates two
  1666   <a href="#dfn-item" class="internalDFN">item</a>s referencing a third item, and how only a single RDF resource definition is created
  1667   for that third item.</p>
  1668 <div class="example"><div class="example-title"><span>Example 18</span></div><pre class="example">&lt;p&gt;
  1669  Both
  1670  &lt;span itemscope itemtype="http://microformats.org/profile/hcard" itemref="home"&gt;
  1671    &lt;span itemprop="fn"
  1672        &gt;&lt;span itemprop="n" itemscope
  1673        &gt;&lt;span itemprop="given-name"&gt;Princeton&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;
  1674   &lt;/span&gt;
  1675  and
  1676  &lt;span itemscope itemtype="http://microformats.org/profile/hcard" itemref="home"&gt;
  1677    &lt;span itemprop="fn"
  1678      &gt;&lt;span itemprop="n" itemscope
  1679        &gt;&lt;span itemprop="given-name"&gt;Trekkie&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;
  1680   &lt;/span&gt;
  1681  live at
  1682  &lt;span id="home" itemprop="adr" itemscope&gt;
  1683    &lt;span itemprop="street-address"&gt;Avenue Q&lt;/span&gt;.
  1684  &lt;/span&gt;
  1685 &lt;/p&gt;</pre></div>
  1687 <p>Assuming that <a href="#dfn-registry" class="internalDFN">registry</a> contains a an entry for <code>http://microformats.org/profile/hcard</code>
  1688   with <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  1689   it generates these triples expressed in Turtle:</p>
  1691 <div class="example"><div class="example-title"><span>Example 19</span></div><pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
  1692 @prefix hcard: &lt;http://microformats.org/profile/hcard#&gt; .
  1693 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
  1695 &lt;&gt; md:item (
  1696   [ a &lt;http://microformats.org/profile/hcard&gt;;
  1697     hcard:fn "Princeton";
  1698     hcard:n [ hcard:given-name "Princeton" ];
  1699     hcard:adr _:a
  1700   ]
  1701   [ a &lt;http://microformats.org/profile/hcard&gt;;
  1702     hcard:fn "Trekkie";
  1703     hcard:n [ hcard:given-name "Trekkie" ];
  1704     hcard:adr _:a
  1705   ]) ;
  1706   rdfa:usesVocabulary &lt;http://microformats.org/profile/hcard&gt; .
  1708 _:a hcard:street-address "Avenue Q" .</pre></div>
  1710 <p>The following snippet of HTML has microdata for a playlist, and illustrates overriding a property
  1711   to place elements in an RDF Collection. This also illustrates the use of the <code>schema:additionalType</code>
  1712   property to relate recordings to the <cite><a href="http://musicontology.com/">Music Ontology</a></cite>:</p>
  1713 <div class="example"><div class="example-title"><span>Example 20</span></div><pre class="example">&lt;div itemscope itemtype="http://schema.org/MusicPlaylist"&gt;
  1714   &lt;span itemprop="name"&gt;Classic Rock Playlist&lt;/span&gt;
  1715   &lt;meta itemprop="numTracks" content="2"/&gt;
  1716   &lt;p&gt;Including works by
  1717     &lt;span itemprop="byArtist"&gt;Lynard Skynard&lt;/span&gt; and
  1718     &lt;span itemprop="byArtist"&gt;AC/DC&lt;/span&gt;&lt;/p&gt;.
  1720   &lt;div itemprop="tracks" itemscope itemtype="http://schema.org/MusicRecording"&gt;
  1721     &lt;link itemprop="additionalType" href="http://purl.org/ontology/mo/MusicalManifestation"/&gt;
  1722     1.&lt;span itemprop="name"&gt;Sweet Home Alabama&lt;/span&gt; -
  1723     &lt;span itemprop="byArtist"&gt;Lynard Skynard&lt;/span&gt;
  1724     &lt;link href="sweet-home-alabama" itemprop="url" /&gt;
  1725    &lt;/div&gt;
  1727   &lt;div itemprop="tracks" itemscope itemtype="http://schema.org/MusicRecording"&gt;
  1728     &lt;link itemprop="additionalType" href="http://purl.org/ontology/mo/MusicalManifestation"/&gt;
  1729     2.&lt;span itemprop="name"&gt;Shook you all Night Long&lt;/span&gt; -
  1730     &lt;span itemprop="byArtist"&gt;AC/DC&lt;/span&gt;
  1731     &lt;link href="shook-you-all-night-long" itemprop="url" /&gt;
  1732   &lt;/div&gt;
  1733 &lt;/div&gt;</pre></div>
  1735 <p>Assuming that <a href="#dfn-registry" class="internalDFN">registry</a> contains a an entry for <code>http://schema.org/</code>
  1736   with <a href="#dfn-propertyuri" class="internalDFN"><code>propertyURI</code></a> set to <code>vocabulary</code>,
  1737   <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> set to <code>unordered</code> with the properties
  1738   <code>track</code> and <code>byArtist</code> having <a href="#dfn-multiplevalues" class="internalDFN"><code>multipleValues</code></a> set to <code>list</code>,
  1739   it generates these triples expressed in Turtle:</p>
  1741 <div class="example"><div class="example-title"><span>Example 21</span></div><pre class="example">@prefix md: &lt;http://www.w3.org/ns/md#&gt; .
  1742 @prefix mo: &lt;http://purl.org/ontology/mo/&gt; .
  1743 @prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt; .
  1744 @prefix rdfa: &lt;http://www.w3.org/ns/rdfa#&gt; .
  1745 @prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt; .
  1746 @prefix schema: &lt;http://schema.org/&gt; .
  1748 &lt;&gt; md:item ([ a schema:MusicPlaylist;
  1749   schema:name "Classic Rock Playlist";
  1750   schema:byArtist ("Lynard Skynard" "AC/DC");
  1751   schema:numTracks "2";
  1752   schema:tracks (
  1753     [ a schema:MusicRecording, mo:MusicalManifestation;
  1754       schema:additionalType mo:MusicalManifestation;
  1755       schema:byArtist ("Lynard Skynard");
  1756       schema:name "Sweet Home Alabama";
  1757       schema:url &lt;sweet-home-alabama&gt;]
  1758     [ a schema:MusicRecording, mo:MusicalManifestation;
  1759       schema:additionalType mo:MusicalManifestation;
  1760       schema:byArtist ("AC/DC");;
  1761       schema:name "Shook you all Night Long";
  1762       schema:url &lt;shook-you-all-night-long&gt;]
  1763   )]);
  1764   rdfa:usesVocabulary schema: .
  1766 schema:additionalType rdfs:subPropertyOf rdf:type .</pre></div>
  1768 </section>
  1770 <section class="appendix informative" id="example-registry">
  1771   <!--OddPage--><h2><span class="secno">C. </span>Example <a href="#dfn-registry" class="internalDFN">registry</a></h2><p><em>This section is non-normative.</em></p>
  1772   <p>The following is an example <a href="#dfn-registry" class="internalDFN">registry</a> in JSON format.</p>
  1774   <div class="example"><div class="example-title"><span>Example 22</span></div><pre class="example">{
  1775   "http://schema.org/": {
  1776     "propertyURI":    "vocabulary",
  1777     "multipleValues": "unordered",
  1778     "properties": {
  1779       "additionalType": {"subPropertyOf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"},
  1780       "blogPosts": {"multipleValues": "list"},
  1781       "blogPosts": {"multipleValues": "list"},
  1782       "breadcrumb": {"multipleValues": "list"},
  1783       "byArtist": {"multipleValues": "list"},
  1784       "creator": {"multipleValues": "list"},
  1785       "episode": {"multipleValues": "list"},
  1786       "episodes": {"multipleValues": "list"},
  1787       "event": {"multipleValues": "list"},
  1788       "events": {"multipleValues": "list"},
  1789       "founder": {"multipleValues": "list"},
  1790       "founders": {"multipleValues": "list"},
  1791       "itemListElement": {"multipleValues": "list"},
  1792       "musicGroupMember": {"multipleValues": "list"},
  1793       "performerIn": {"multipleValues": "list"},
  1794       "actor": {"multipleValues": "list"},
  1795       "actors": {"multipleValues": "list"},
  1796       "performer": {"multipleValues": "list"},
  1797       "performers": {"multipleValues": "list"},
  1798       "producer": {"multipleValues": "list"},
  1799       "recipeInstructions": {"multipleValues": "list"},
  1800       "season": {"multipleValues": "list"},
  1801       "seasons": {"multipleValues": "list"},
  1802       "subEvent": {"multipleValues": "list"},
  1803       "subEvents": {"multipleValues": "list"},
  1804       "track": {"multipleValues": "list"},
  1805       "tracks": {"multipleValues": "list"}
  1806     }
  1807   },
  1808   "http://microformats.org/profile/hcard": {
  1809     "propertyURI":    "vocabulary",
  1810     "multipleValues": "unordered"
  1811   },
  1812   "http://microformats.org/profile/hcalendar#": {
  1813     "propertyURI":    "vocabulary",
  1814     "multipleValues": "unordered",
  1815     "properties": {
  1816       "categories": {"multipleValues": "list"}
  1817     }
  1818   }
  1819 }</pre></div>
  1820 </section>
  1822 <section class="appendix informative" id="acknowledgements">
  1823   <!--OddPage--><h2><span class="secno">D. </span>Acknowledgements</h2><p><em>This section is non-normative.</em></p>
  1824   <p>Thanks to Richard Cyganiak for property URI and vocabulary terminology and the general excellent
  1825     consideration of practical problems in generating RDF from microdata.</p>
  1826 </section>
  1830 <section id="references" class="appendix"><!--OddPage--><h2><span class="secno">E. </span>References</h2><section id="normative-references"><h3><span class="secno">E.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> 29 March 2012. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/html5">http://www.w3.org/TR/html5</a> 
  1831 </dd><dt id="bib-MICRODATA">[MICRODATA]</dt><dd><cite><a href="http://www.w3.org/TR/2012/WD-microdata-20120329/">HTML Microdata</a></cite> Ian Hickson Editor. W3C Working Draft. (Work in progress). 29 March 2012. This edition of the HTML Microdata specification is http://www.w3.org/TR/2012/WD-microdata-20120329/. The <a href="http://www.w3.org/TR/microdata/">latest edition of HTML Microdata</a> is available at http://www.w3.org/TR/microdata/
  1832 </dd><dt id="bib-OWL2-OVERVIEW">[OWL2-OVERVIEW]</dt><dd>W3C OWL Working Group. <a href="http://www.w3.org/TR/2009/REC-owl2-overview-20091027/"><cite>OWL 2 Web Ontology Language: Overview.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-overview-20091027/">http://www.w3.org/TR/2009/REC-owl2-overview-20091027/</a> 
  1833 </dd><dt id="bib-OWL2-PROFILES">[OWL2-PROFILES]</dt><dd>Boris Motik; Bernardo Cuenca Grau; Ian Horrocks; Zhe Wu; Achille Fokoue; Carsten Lutz. <a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/"><cite>OWL 2 Web Ontology Language:Profiles.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/">http://www.w3.org/TR/2009/REC-owl2-profiles-20091027/</a> 
  1834 </dd><dt id="bib-OWL2-RDF-BASED-SEMANTICS">[OWL2-RDF-BASED-SEMANTICS]</dt><dd>Michael Schneider. <a href="http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/"><cite>OWL 2 Web Ontology Language:RDF-Based Semantics.</cite></a> 27 October 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/">http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/</a> 
  1835 </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> 
  1836 </dd><dt id="bib-RDF-MT">[RDF-MT]</dt><dd>Patrick Hayes. <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210"><cite>RDF Semantics.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-mt-20040210">http://www.w3.org/TR/2004/REC-rdf-mt-20040210</a> 
  1837 </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> 
  1838 </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> 
  1839 </dd></dl></section><section id="informative-references"><h3><span class="secno">E.2 </span>Informative references</h3><dl class="bibliography"><dt id="bib-MICRODATA-RDF-SUPPLEMENT">[MICRODATA-RDF-SUPPLEMENT]</dt><dd><cite><a href="http://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-supplement/index.html">Microdata to RDF Supplement</a></cite> Gregg Kellogg Editor. World Wide Web Consortium (work in progress). 22 January 2012.
  1840 </dd><dt id="bib-MICRODATA-RDF-TESTS">[MICRODATA-RDF-TESTS]</dt><dd><cite><a href="http://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/tests/index.html">Microdata to RDF Tests</a></cite> Gregg Kellogg, Ivan Herman Editors. World Wide Web Consortium (work in progress). 22 March 2012.
  1841 </dd><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> 
  1842 </dd><dt id="bib-RDFA-CORE">[RDFA-CORE]</dt><dd>Shane McCarron; et al. <a href="http://www.w3.org/TR/2012/REC-rdfa-core-20120607/"><cite>RDFa Core 1.1: Syntax and processing rules for embedding RDF through attributes.</cite></a> 7 June 2012. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2012/REC-rdfa-core-20120607/">http://www.w3.org/TR/2012/REC-rdfa-core-20120607/</a> 
  1843 </dd></dl></section></section></body></html>