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Re: NEWBIE: Property restriction semantics

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Tue, 17 Feb 2004 12:44:52 -0500 (EST)
Message-Id: <20040217.124452.106057462.pfps@research.bell-labs.com>
To: kotsomit@hpclab.ceid.upatras.gr
Cc: public-webont-comments@w3.org

From: "Dimitrios A. Koutsomitropoulos" <kotsomit@hpclab.ceid.upatras.gr>
Subject: RE: NEWBIE: Property restriction semantics
Date: Tue, 17 Feb 2004 19:27:09 +0200

> 
> Thanks indeed! It seems more clear now. However...
> 
> > -----Original Message-----
> > From: public-webont-comments-request@w3.org 
> > [mailto:public-webont-comments-request@w3.org] On Behalf Of 
> > Peter F. Patel-Schneider
> > Sent: Tuesday, February 17, 2004 5:49 PM
> > To: kotsomit@hpclab.ceid.upatras.gr
> > Cc: public-webont-comments@w3.org
> > Subject: Re: NEWBIE: Property restriction semantics
> > 
> > 
> > From: "Dimitrios A. Koutsomitropoulos" 
> > <kotsomit@hpclab.ceid.upatras.gr>
> > Subject: Re: NEWBIE: Property restriction semantics
> > Date: Tue, 17 Feb 2004 17:26:09 +0200
> > 
> > > 
> > > 
> > > Let's consider the following modification of Brian's example:
> > > 
> > > 
> > > <owl:Class rdf:ID="Student"/>
> > > 
> > > <owl:ObjectProperty rdf:ID="hasGrade">  <rdfs:domain 
> > > rdf:resource="#Student"/>  <rdfs:range rdf:resource="#Grade"/> 
> > > </owl:ObjectProperty>
> > > 
> > > <owl:Class rdf:ID="FailedStudent">
> > >  <rdfs:subClassOf rdf:resource="#Student"/>  <owl:equivalentClass>  
> > > <!-- instead of subClassOf -->
> > >    <owl:Restriction>
> > >      </owl:onProperty rdf:resource="#hasGrade"/>
> > >      </owl:hasValue rdf:resource="#Failed"/>
> > >    </owl:Restriction>
> > >  </owl:subClassOf>
> > > </owl:Class>
> > > 
> > > And just assert that Brian isA FailedStudent:
> > > 
> > > <FailedStudent rdf:ID="Brian" />
> > > 
> > > Would this imply that Brian hasGrade Failed?
> 
> ...by "Brian hasGrade Failed" I do not mean that "Brian in hasGrade:Failed"
> which I can understand. I mean if the actual role filler for instance:Brian
> and Role:hasGrade will be the instance:Failed.

Well, you are now going beyond the logic.  As far as the logic is concerned

	Brian in hasGrade:Failed

is how you say that Brian's grade is Failed so there is no distinction
that can be made in the logic.

> For example, Racer does not seem to infer this...

Perhaps RACER makes a distinction between actual fillers and inferred
concept membership.  This is not sanctioned by the logic, so RACER is on
its own here.

> > Yes.  Note, however, that this inference would also be valid 
> > in the original example.  Note also that your example doesn't 
> > make much sense, as it has lots of unusual consequences.
> > 
> > This is yet another case where the RDF/XML syntax is not 
> > helpful, as it obscures the real semantic relationships.  
> > What you have done is define FailedStudent as follows
> > 
> > 
> > 	FailedStudent <= Student
> > 	FailedStudent = hasGrade : Failed
> > 
> > >From this you can infer
> > 
> > 	hasGrade:Failed <= Student
> > 
> > i.e., any thing that has a failing grade (perhaps in love, 
> > for example) would be a Student.  What you probably want is
> > 
> > 	FailedStudent = Student & hasGrade:Failed
> > 
> > or
> > 
> > 	FailedStudent <= Student & hasGrade:Failed
> > 
> > In both these cases
> > 
> > 	Brian in FailedStudent
> > 
> > implies
> > 
> > 	Brian in hasGrade:Failed
> > 
> > 
> > > I would be really happy for any feedback on this!
> > > 
> > > Many thanks,
> > > 
> > > 
> > > Dimitris Koutsomitropoulos
> > 
> > Peter F. Patel-Schneider
> > 
> > 
> 
Received on Tuesday, 17 February 2004 12:45:22 UTC

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