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Re: need to determine what RDF is

From: patrick hayes <phayes@ai.uwf.edu>
Date: Thu, 30 May 2002 11:10:15 -0500
Message-Id: <p0511172ab91bfd4e11d5@[65.217.30.61]>
To: Dan Connolly <connolly@w3.org>
Cc: danbri@w3.org, bwm@hplb.hpl.hp.com, www-rdf-comments@w3.org, em@w3.org, w3c-semweb-cg@w3.org, pfps@research.bell-labs.com

>On Thu, 2002-05-30 at 10:26, Peter F. Patel-Schneider wrote:
>[...]
>>  I'm only interested in relationships between RDF graphs.  Which such
>>  relationships are RDF relationships? 
>>
>>  My view is that the only such relationships are RDF entailment and RDFS
>>  entailment.  Any agent that computes any other relationship between RDF
>>  graphs is not doing RDF.
>
>Why is RDFS special? It's just the first of many RDF vocabularies,
>no?

Its more than just an RDF vocabulary because it has some extra 
semantic conditions. For example, if RDFS is considered purely as an 
RDF vocabulary, then rdfs:subClassOf is not required to be 
transitive; in fact, there is no way to express transitivity of a 
property in RDF. Considered as RDFS, however, it is required to be 
transitive. The distinction is made exact in the MT document by 
distinguishing between RDF-entailment and RDFS-entailment. In 
general, if a particular vocabulary has some extra semantic 
conditions attached to it, then there will be a new notion of 
entailment (I used the generic term 'vocabulary entailment' for this 
idea in the MT document: 
http://www.w3.org/TR/rdf-mt/#NameSpaceEntailment ). Most RDF 
vocabularies, eg dublin core, RSS, have no extra semantics attached 
to them. DAML+OIL certainly does, of course, but then I wouldn't even 
call that an RDF vocabulary in any ordinary sense (yet).

RDFS is also special because its specified in the RDF specs, I guess.

Pat

>I could understand a definition that said 'anybody doing more than
>RDF simple entailments isn't doing RDF', but I don't understand
>a definition of RDF that includes RDFS but not dublin core,
>RSS, DAML+OIL/OWL, etc.
>
>>   (Well, actually, I suppose that an agent could be
>>  determining whether two RDF graphs RDF entail each other, which is
>>  different from RDF entailment, but I think that you should be able to get
>>  my drift.)
>>
>>  peter
>--
>Dan Connolly, W3C http://www.w3.org/People/Connolly/


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Received on Thursday, 30 May 2002 12:10:11 GMT

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