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Re: TEST: 6 of 7: empty universe example,

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 23 Jul 2003 21:29:11 -0400 (EDT)
Message-Id: <20030723.212911.63244984.pfps@research.bell-labs.com>
To: jos.deroo@agfa.com
Cc: jjc@hpl.hp.com, www-webont-wg@w3.org, www-webont-wg-request@w3.org

From: "Jos De_Roo" <jos.deroo@agfa.com>
Subject: Re: TEST: 6 of 7: empty universe example,
Date: Thu, 24 Jul 2003 01:07:25 +0200

> 
> Peter F. Patel-Schneider wrote:
> > From: Jeremy Carroll <jjc@hpl.hp.com>
> > Subject: TEST: 6 of 7: empty universe example,
> > Date: Wed, 23 Jul 2003 19:20:15 +0300
> >
> > >
> > > Peter?
> > > (for book-keeping)
> > >
> > > I had some outstanding actions on this one.
> > >
> > > At one point it seemed that I would need to make owl:Thing finite but
> > > non-empty to get different behaviour in DL and Full; it now appears
> that
> > > owl:Thing can be empty in DL, os I have reduced the test to
> > >
> > > owl:Thing owl:equivalentClass owl:Nothing
> > >
> > >
> http://www.w3.org/2002/03owlt/editors-draft/draft/proposedByFunction#Thing-001
> 
> > >
> http://www.w3.org/2002/03owlt/editors-draft/draft/proposedByFunction#Thing-002
> 
> > >
> > > this test is slightly different from the one that I was actioned to
> produce.
> > >
> > > Jeremy
> >
> > Hmm.  There may have been a slight glitch here at some time.
> >
> > Right now, neither the direct semantics nor the rdfs semantics require
> that
> > the OWL DL universe of discourse is non-empty.
> >
> > As Pat pointed out empty universes can cause problems in languages with
> > quantification.  I don't think that these problems surface in OWL.
> 
> 
> I really can't make any sense of following being consistent
> 
> [[
> <rdf:RDF
>     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>     xmlns:owl="http://www.w3.org/2002/07/owl#"
>     xml:base="http://www.w3.org/2002/03owlt/Thing/consistent001" >
> 
>   <owl:Class rdf:about="http://www.w3.org/2002/07/owl#Thing">
>     <owl:equivalentClass rdf:resource
>        ="http://www.w3.org/2002/07/owl#Nothing"/>
>   </owl:Class>
> 
> </rdf:RDF>
> ]]
> 
> which is basically and globally the content of
> http://www.w3.org/2002/03owlt/Thing/consistent001
> (but it's currently forbidden to access it
> and maybe it better stay's like that ;-))
> 
> 
> > peter
> --
> Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/

Well, I agree that it is a silly thing to say, but it is (currently) not
inconsistent in OWL DL.  Remember that in OWL DL there are no built-in
individuals.


peter
Received on Wednesday, 23 July 2003 21:29:25 GMT

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