View source for Mapping Microdata to RDF

This page describes how microdata content can be consumed by a consumer whose back-end systems are based on an RDF (or RDF-like) model, as part of the work of the [[Html-data-tf|HTML Data TF]].

Transformation description moved to [https://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/index.html ReSpec document]

== Property URI generation ==
Microdata allows properties to be specified as simple names, which then have a URI generation rule applied to them. As different vocabularies have different
requirements for property URIs, the idea is to provide a way to inform the processor of how to generate URIs, and have the processor fall back to a specific
URI generation strategy if no other information is available.

There are  different strategies for generating property URIs from names:
;hashSlash
: Infer the vocabulary from the @itemtype, and append the name to the resulting vocabulary URI. This would take advantage of the typically RDF strategy of having a flat namespace for classes and properties, so that the class name could be removed from the @itemtype URI to which the name can be appended. For example, if the type were <code>http://schema.org/Thing</code> the property 'name' would be be <code>http://schema.org/name</code>. Types are inherited by items without an @itemtype. Items without a type (explicit or inherited) append the name to the document base URI, in the case that the item has no type. For example, if the document had a base of <code>http://example.com/doc</code>, name could be appended along with a '#', yielding <code>http://example.com/doc#name</code>
;fragID
: Append the name to the @itemtype URI. For example, given the URI <code>http://microformats.org/profile/hcard</code> as the type, the property 'fn' would result in the following URI: <code>http://microformats.org/profile/hcard#fn</code>. Note this is only possible if the type does not include a '#', which would result in an error and/or no generated property URI.
;contextual
: Append the name to a combination of @itemtype and the property path, and ensure that property URIs generated from names are distinct from explicit property URIs. For example, given the type <code>http://microformats.org/profile/hcard</code>, the property 'fn' would result in <code>http://www.w3.org/1999/xhtml/microdata#http://microformats.org/profile/hcard#:%23fn</code>. However, if there is an intervening item without a type, it would construct a different URI. Assuming an intervening property 'foo', the resulting URI would be <code>http://www.w3.org/1999/xhtml/microdata#http://microformats.org/profile/hcard#:%23foo%20fn</code>.

These strategies can be the value of a _propertyURIGeneration_ parameter added to the initial evaluation context.

=== Vocabulary-specific URI generation ===
A registry may associate different vocabularies with property URI generation schemes, for example:

<pre>
<http://schema.org/> a :Vocabulary; :propertyURIscheme :slashHash .
<http://microformats.org/profile/hcard> a :Vocabulary; :propertyURIscheme :contextual .
</pre>

A vocabulary-aware processor could then change URI generation schemes when encountering @itemtype URIs contained in the registry, and fallback to a default setting otherwise.

== Multiple types for an item ==

TBD.

== Examples ==
Additional examples can be added here.

An example of a  a http://schema.org/Organization that is the provider, publisher and copyrightHolder of a http://schema.org/NewsArticle. 
When converting this sample to RDF, it might be interesting that the "itemid" of the Organization object happens to be the same URL that is used as a property expecting a URL (the "url" property of http://schema.org/Thing in this case) from the same object. The "url" property of http://schema.org/Thing is not meant to take a http://schema.org/Organization as a value, but a URL.    

<pre>
<body itemscope="itemscope" itemtype="http://schema.org/NewsArticle"
  itemid="http://www.businesswire.com/news/home/20110106006854/en">
...
<span itemprop="provider publisher copyrightHolder" itemscope="itemscope"
          itemtype="http://schema.org/Organization" itemid="http://businesswire.com">
  <meta itemprop="name" content="Business Wire"/>
  <a itemprop="url" href="http://www.businesswire.com">
     <img itemprop="image"
              src="http://www.businesswire.com/images/Powered-by-Business-Wire.gif"
              title="Business Wire is the leading source for full-text breaking news and press releases, 
              multimedia and regulatory filings for companies and groups throughout the world"
              alt="Powered by Business Wire"/>
  </a>
</span>
...
</body>
</pre>


The resulting RDF from this example is:
<pre>
<http://www.businesswire.com/news/home/20110106006854/en> a schema:NewsArticle;
 schema:copyrightHolder <http://www.businesswire.com> .


<http://businesswire.com> a schema:Organization;
   schema:image <http://www.businesswire.com/images/Powered-by-Business-Wire.gif>;
   schema:name "Business Wire";
   schema:url <http://www.businesswire.com> .
</pre>



[[Category:HTML Data TF]]