From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>

Date: Fri, 09 May 2003 16:37:33 -0400 (EDT)

Message-Id: <20030509.163733.125987127.pfps@research.bell-labs.com>

To: www-webont-wg@w3.org

Cc: jjc@hplb.hpl.hp.com

Date: Fri, 09 May 2003 16:37:33 -0400 (EDT)

Message-Id: <20030509.163733.125987127.pfps@research.bell-labs.com>

To: www-webont-wg@w3.org

Cc: jjc@hplb.hpl.hp.com

Jeremy has pointed out a problem with the semantics. The semantics assumes that intersectionOf is a ``syntactic'' relationship, i.e., there are no sufficient conditions for it. This was fine once upon a time, but is now, due to recent changes in the mapping to triples, the correspondence theorem is now not correct. There are several possible changes: 1/ Change the mapping back to the way it was, so that, for example, classes are not related to their ``definition'' by owl:intersectionOf relationships. Instead there would be an anonymous intersection class related to the named class by an equivalence link. This would be the safest course. 2/ Leave the mapping the way it is and upgrade owl:intersectionOf from a syntactic relationship to a semantic one. This would require significant work on the correspondence proofs. (If this course is taken I would withdraw my action to look into B1 and B2.) 3/ peter From: "Jeremy Carroll" <jjc@hplb.hpl.hp.com> Subject: RE: intersectionOf and subClassOf Date: Thu, 10 Apr 2003 17:12:51 +0200 > > I think S&AS may be wrong about this. > > Peter: > [[ > Because of OWL's embedding on top of RDF there are actually several > options that could arise here. > > 1/ One could have the semantic constraint on owl:intersectionOf > that if the extension of x is the same as the intersection of the > extensions of a and b then x owl:intersectionOf [a b] > 2/ One could have the semantic constraint that if > x owl:intersectionOf [a b] then the extension of x is the same > as the intersection of the extensions of a and b > 3/ One could have the semantic constraint that if > x owl:intersectionOf [a b] then the extension of x is a subset > of the intersection of the extensions of a and b > ]] > > Option 1 might have been a better choice than option 2 (if I understood > Peter's earlier message) > > E.g. > > Consider > > <owl:Class rdf:about="#AandB"> > <owl:equivalentClass> > <owl:Class> > <owl:intersectionOf rdf:parseType="Collection"> > <owl:Class rdf:about="#A"/> > <owl:Class rdf:about="#B"/> > </owl:intersectionOf> > </owl:Class> > </owl:equivalentClass> > </owl:Class> > > This corresponds to the abstract syntax form > > EquivalentClasses(<#AandB> intersectionOf(<#A> <#B>) ) > > which directly entails > > Class( <#AandB> complete <#A> <#B> ) > > which corresponds to > > > <owl:Class rdf:about="#AandB"> > <owl:intersectionOf rdf:parseType="Collection"> > <owl:Class rdf:about="#A"/> > <owl:Class rdf:about="#B"/> > </owl:intersectionOf> > </owl:Class> > > > i.e. option 1 > > but the rdfs compatible semantics has taken option 2. > > Is this a bug? > Does someone need to make a last call comment? > Or have I misunderstood? > > Jeremy >Received on Friday, 9 May 2003 18:53:25 UTC

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