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Re: RDF/XML and CURIEs

From: Ivan Herman <ivan@w3.org>
Date: Mon, 10 Mar 2008 17:03:35 +0100
Message-ID: <47D55BD7.4040300@w3.org>
To: Shane McCarron <shane@aptest.com>
CC: "public-rdf-in-xhtml-tf.w3.org" <public-rdf-in-xhtml-tf@w3.org>
Hi Shane,

congratulations! You have discovered one of the nasty little secrets 
about RDF/XML, namely that there are perfectly valid RDF graphs that 
cannot be encoded into RDF/XML. This is a known problem, filed as an 
official unsolved issue for RDF/XML that a future RDF group (if such an 
animal will be created) will have to take care of.

Note that the same RDF graph can be expressed in NTriples and in Turtle 
without any problem. And, well, in some ways, in RDFa (except that the 
RDFa parser should output Turtle, for example, to be o.k.).

So: if by 'we' you mean the RDFa group, then the answer is indeed that 
we do not care. If by 'we' you mean the Semantic Web activity than, 
well, yes we have to care about serializations in general...

Ivan

B.t.w.: this is the very problem Misha Wolf and IPTC had for a long time...

Shane McCarron wrote:
> 
> Okay.... Someone please tell me I am wrong about the following:
> 
> When trying to force my RDFa parser to emit RDF/XML so it will work with 
> the test suite, I noticed that the general model for RDF/XML is that 
> predicates are expressed as elements.  E.g. a property of "foaf:name" in 
> RDFa would map to an element <foaf:name> in RDF/XML.  And somewhere the 
> foaf namespace would be declared.  So far so good.
> 
> Then I started thinking about our extension model and CURIEs.   If I use 
> one of our existing examples about isbn numbers..... let's say I declare 
> xmlns:amazon="http://www.amazon.com/books?isbn="  and in my RDFa I have 
> something like <span property="amazon:12345">My Book Title</span>
> 
> I think that we generate a triple where the predicate is amazon:12345, 
> or http://www.amazon.com/books?isbn=12345 - again, so far so good.
> 
> But, if I want to map that into RDF/XML, I need to do something like:
> 
>    <amazon:12345>My Book Title</amazon:12345>
> 
> Sadly, that is invalid.
> Please, someone tell me I am wrong.  Alternately, someone tell me we 
> don't care.
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Monday, 10 March 2008 16:03:41 UTC

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