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Gregg Kellogg
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Semantic Media Consultant
Semantic Media Consultant

110 followers
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In The RDFa working group, we discussed how we might add support for something like microdata's @itemref property. Itemref allows statements to be made separate from the rest of an item, and referenced from one ore more scopes. It's popular in microdata, because it helps a pattern, often used for Good Relations product definitions, where all of the products are the same, except for a couple of properties, such as size and color.

Simply tacking this on to RDFa is difficult, because RDFa is designed to be stream processed, and doesn't depend on doing DOM manipulation. However, RDFa does have a powerful optional feature, called Vocabulary Expansion. This is mostly intended to allow vocabulary definitions to make statements about sub-classes and sub-properties, but it can be used to similar effect for this purpose.

We define a new property and class as follows: rdfa:Prototype is the type of a resource the can be referenced via an rdfa:ref. This then invokes the following expansion/deletion rules:

INSERT DATA {
 ?x ?p ?y .
}
DELETE DATA {
 ?x rdfa:ref ?PR .
 ?x a rdfa:Prototype .
 ?PR ?p ?y .
}
WHERE {
 ?x rdfa:ref ?PR .
 ?PR ?p ?y.
 ?PR a rdfa:Prototype .
}

As opposed to microdata, the RDFa approach makes use of a resource with the type rdfa:Prototype, so the reference is done as a regular property reference using the rdfa:ref property. For example, consider the following simple example:

         <div>
           <div typeof="schema:Person">
             <link property="rdfa:ref" resource="_:a"/>
           </div>
           <p resource="_:a" typeof="rdfa:Prototype">Name: <span property="schema:name">Amanda</span></p>
         </div>

should produce

         @prefix schema: <http://schema.org/> .
         [a schema:Person; schema:name "Amanda"] .

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This article describes work I've been engaged in with Wikia for the past couple of months. This is the basis for the presentation I'm giving this Thursday at NoSQL Now! on JSON-LD.

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Slides done for my talk this Thursday at NoSQL Now! on JSON-LD and MongoDB for enabling single-page web apps.

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Some results from a couple of dives of Santa Cruz Island over Memorial Day weekend. I was mostly teaching, but I had a couple of dives free to engage in my passion.
PhotoPhotoPhotoPhotoPhoto
Channel Islands May 2012
19 Photos - View album

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New blog post on the use of #BrowserID to thwart a DDOS attack on the #RDFa test suite.

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More on the RDFa Test Suite. This time generating EARL reports and how #JSON-LD compliments #RDFa.

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New blog post on implementing the new RDFa Test Harness. First in a series.

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A small SPARQL endpoint in Ruby.

Check out the blog post at http://greggkellogg.net/2012/02/09/rdf-rb-0-3-5-and-sparql-0-1-0 for how to use the Ruby SPARQL gem to run a minimal SPARQL endpoint using Sinatra.

This is now running on my RDF Distiller at http://rdf.greggkellogg.net/sparql

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Breaking: W3C launches new HTML5 validation service supporting RDFa 1.1 Lite and RDFa 1.1 Full: http://ow.ly/8WZp2 #rdfa #html5 /via +Ivan Herman
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