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More specific proposal on the vocabulary expansion (a.k.a. vocab proxy) feature

From: Ivan Herman <ivan@w3.org>
Date: Thu, 4 Aug 2011 18:33:34 +0200
To: W3C RDFWA WG <public-rdfa-wg@w3.org>
Message-Id: <872656B4-4527-4699-90C8-49529E9C7E34@w3.org>

I have had a long discussion with Manu today, and we both agreed that, in view of all the issues surrounding RDFa and its future, it would be good to 'spec' the proxy feature as soon as possible to move ahead. I had a very first stab at it, which is clearly not spec quality but at least gathers my thoughts on how this thing could be specified relatively quickly and succinctly. My goal was to try to minimize what *we* should specify and, rather, rely on existing specifications. We may want to check that with some people who are good at semantics.

Here it is.



<h1>RDFa Vocabulary Expansion</h1>

Once the default graph is generated following the processing steps defined at @@LINK@@, RDFa processors MAY (or SHOULD?) perform the following processing steps on the default graph.

- For all URI-s that appear as a value of a @vocab attribute in the RDFa source, that URI is dereferenced. If the dereferencing yields the serialization of an RDF graph, that graph is merged with the default graph. (RDFa processor MUST accept an RDF graph serialized in RDFa, SHOULD accept an RDF graph serialized in RDF/XML[REF] or Turtle[REF], and MAY accept other serialization formats of RDF.) 
- The processor expands the default graph using the RDFa Vocab Entailment @@@Link to section below@@@.

<h2>RDFa Vocab Entailment</h2>

<h3>RDFa Vocab Entailment definition (normative)</h3>

For the purpose of vocabulary processing, RDFa uses restricted version of the full RDFS entailment[1]. This entailment is based on a restriction of the vocabulary used by the RDFS Interpretation[2]. Indeed, the RDFa vocab entailment vocabulary contains only the following terms:

- rdf:type rdfs:subClassOf rdfs:subPropertyOf

and the RDFa vocabulary entailment does not use any of the axiomatic triples defined in [2] or [3].

<h3>RDFa Vocab Entailment Rules (informative)</h3>

While the formal definition of the RDFa Entailment is defined in terms of RDF Semantics, practical implementations may rely on the (informative) entailement rules published in the RDF Semantics documents[4]. In particular, the relevant rules are (using the rule identification in [4]): rdfs5, rdfs7, rdfs9, and rdfs11.  

<h2>Vocabulary Expansion Contol of RDFa Processors</h2>

Comforming RDFa processors are <em>not</em> required to provide vocabulary expansion. 

If an RDFa processor provides vocabulary expansion, it MUST NOT be done by default. Instead, the processor must provide an option, <tt>vocab_expansion</tt>, which, when used, instructs the RDFa processor to perform a vocabulary expansion before returning the default graph.

[1] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#rdfs_entailment
[2] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#rdfs_interp
[3] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#InterpVocab
[4] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#rules

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
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Received on Thursday, 4 August 2011 16:31:46 UTC

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