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Re: Suggestion for Microdata to RDF conversion

From: Philip Jägenstedt <philipj@opera.com>
Date: Thu, 21 Jan 2010 00:41:15 +0100
To: bnowack@semsol.com, public-html@w3.org
Message-ID: <op.u6uuq1xksr6mfa@worf>
On Tue, 19 Jan 2010 18:17:19 +0100, Benjamin Nowack <bnowack@semsol.com>

> Hi,
> I'm working on a Microdata parser as part of an RDF toolkit. One thing
> I've implemented but that isn't directly stated in the draft is the
> generation of property URIs in the context of the itemtype. The spec
> mentions that plain properties are to be used "within the context of
> the types for which they are intended". And RDF vocabularies follow
> the {namespace}/{type|prop} or {namespace}#{type|prop} pattern. So,
> I made my parser extract the following RDF triples:
>   _:bnode a <http://xmlns.com/foaf/0.1/Person> .
>   _:bnode <http://xmlns.com/foaf/0.1/name> "Alec Tronnick" .
>   _:bnode <http://xmlns.com/foaf/0.1/img> <mypic.jpg> .
> from the Microdata snippet:
>   <div itemscope="" itemtype="http://xmlns.com/foaf/0.1/Person">
>     My name is <span itemprop="name">Alec Tronnick</span>
>     <img itemprop="img" src="mypic.jpg" alt="" />
>   </div>
> as "name" and "img" are supposed to be applicable to the "Person"
> type from the FOAF vocabulary. This sort of rule leads to very
> compact markup in most single-vocab use cases (even more compact
> and readable than RDFa's CURIEs) and simple authoring.
> A sophisticated parser *could* GET and check the RDF vocabulary
> for valid use of properties, but RDF does not have instance-level
> validation, so the transparent expansion of plain property names
> does not conflict with the RDF spec(trum). An author can of
> course still use full URIs to mix in terms from other vocabs.

If you follow the conversion algorithm at  
<http://dev.w3.org/html5/md/#rdf>, you'll find that your markup yields  
something like these triples:

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
_:n0 rdf:type <http://xmlns.com/foaf/0.1/Person> ;
"Alec Tronnick" ;
<http://example.com/mypic.jpg> .
<http://www.w3.org/1999/xhtml/microdata#item> _:n0 .

Note especially that mypic.jpg is resolved, here I assumed the markup was  
 from http://example.com/foo.html.

To produce the triples you wanted, use this markup:

<div itemscope="" itemtype="http://xmlns.com/foaf/0.1/Person">
   My name is <span itemprop="http://xmlns.com/foaf/0.1/name">Alec  
   <img itemprop="http://xmlns.com/foaf/0.1/img" src="mypic.jpg" alt="" />

As you can see, microdata has no prefix notation. To save yourself some  
typing, use this:

<div itemscope itemtype="http://microformats.org/profile/hcard">
   My name is <span itemprop="fn">Alec Tronnick</span>
   <img itemprop="photo" src="mypic.jpg" alt="">

If you actually wanted to use FOAF or care very much about the exact  
triples, then the OWL needed to map the above to vCard RDF shouldn't be  
very tricky, and I assume the relationship between FOAF and that is  
already pretty clear.

Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 20 January 2010 23:41:49 UTC

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