From: Ian Horrocks (horrocks@cs.man.ac.uk)
Date: 07/10/01
On July 9, pat hayes writes: > >On Mon, 9 Jul 2001, Jeff Heflin wrote: > > > > > Ian Horrocks wrote: > > > > > > > > On July 7, Dan Brickley writes: > > > > > > > > > > I was concerned mostly with the classes case as I'm thinking about the > > > > > subClassOf cycles issue. Reading on, same goes for samePropertyAs, > > > > > sameIndividualAs; it seems equivalentTo is the odd one out, by talking > > > > > about 'terms'. > > > > > > > > You are reading more into the use of "terms" than was intended. It is > > > > just an attempt to be vague/general w.r.t. the kinds of thing that are > > > > being stated to be equivalent. > > > > > > > > > > I think the definition for equivalentTo should say that "X is an > > > equivalent resource to Y," where resource is as defined in RDF. Since > > > RDF resources can be classes, properties or anything else given a URI, > > > this is compatible with the various subproperties of equivalentTo. > > > sameIndividualAs is different from equivalentTo because the set of DAML > > > individuals do not include classes or properties. > > > >Aha! That's it. From reading the spec, it wasn't entirely clear to me > >what DAML+OIL terms individuals. The schema definition suggests its a > >synonym for 'thing': > > > > <Property rdf:ID="sameIndividualAs"> > > <rdfs:label>sameIndividualAs</rdfs:label> > > <rdfs:comment> > > for sameIndividualAs(a, b), read a is the same individual as b. > > </rdfs:comment> > > <rdfs:subPropertyOf rdf:resource="#equivalentTo"/> > > <rdfs:domain rdf:resource="#Thing"/> > > <rdfs:range rdf:resource="#Thing"/> > > </Property> > > > >Could someone explain to me which things precisely are considered > >individuals? I gather properties and classes are out of the > >picture. Any others? > > My understanding is that 'individual' is synonymous with 'DAML+OIL > object' and simply means anything in the semantic domain. The use of > 'individual' for anything in the domain of quantification is a > familiar convention in logic, but maybe it needs to be spelled out > for a wider audience. I don't believe this is quite correct. As far as I am concerned, the denotation of an individual is an object in the domain of discourse, and there is nothing to prevent two individuals from denoting the same object (this is what sameIndividualAs asserts). Ian
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