- From: Ian Horrocks <horrocks@cs.man.ac.uk>
- Date: Thu, 28 Aug 2003 08:46:23 +0100
- To: Dan Connolly <connolly@w3.org>
- Cc: Steven Gollery <sgollery@cadrc.calpoly.edu>, www-rdf-logic@w3.org
On August 27, Dan Connolly writes: > > On Wed, 2003-08-27 at 12:39, Steven Gollery wrote: > > In DAML: > > > > if there is a property P1 whose domain is class C1 and range is class C2 > > I presume you mean to use domain/range in the sense > of rdfs:domain and rdfs:range; i.e. C1 is *a* range > of P1 and C2 is *a* range of P1. i.e. > forall X, Y, if P1(X, Y) then X in C1 and Y in C2. > > and *not* the other fairly common usage of range, i.e. > for all Y, if Y in C2 then there is some X with P1(X, Y). > > > and there is a property P2 whose domain is class C3 and range is class > > C4 > > and there is a statement that P1 is the samePropertyAs P2, > > > > does it follow that C1 is the sameClassAs C3 and C2 is the sameClassAs > > C4, > > no. Counterexample: > eats rdfs:domain Animal; rdfs:range Food.# P1/C1/C2 > consumes rdfs:domain rdf:Resource; rdfs:range rdfs:Resource.# P2/C3/C4 > > Now we can have > eats daml:samePropertyAs consumes. #i.e. same extension > but lots of things can be in rdf:Resource without > begin in Animal nor Food. > > > > > or does it just add a new class to the domain and range of each of > > the properties? > > Umm... no, I don't think so; I'm not even sure what that means. > > > Or neither one? > > It just means that P1 and P2 have the same property extension. > i.e. for every X and Y, P1(X,Y) iff P2(X,Y). Yes, and this means that for every x, if there exists some y s.t. P1(x,y) (or P2(x,y)), then x has type (intersectionOf C1 C3), and y has type (intersectionOf C2 C4). The semantics of DAML+OIL do not make it completely clear if (domain P1 (intersectionOf C1 C3)) and (range P1 (intersectionOf C2 C4)) (and the same for P2) are entailed. However, this *is* the case in OWL, i.e., the intersection domain and range restrictions are entailed. As Dan points out, the fact that the domain of P1 is (intersectionOf C1 C3) does *not* entail that C1 and C3 are equivalent. Ian > > fyi, the OWL equivalent of daml:samePropertyAs > is owl:equivalentProperty. > > cf > > 4.2.1 owl:equivalentProperty > http://www.w3.org/TR/2003/CR-owl-ref-20030818/#equivalentProperty-def > > and the links to the other parts of the specification > that discuss equivalentProperty in > > Appendix C. OWL Quick Reference > http://www.w3.org/TR/2003/CR-owl-ref-20030818/#appC > > > -- > Dan Connolly, W3C http://www.w3.org/People/Connolly/ > >
Received on Thursday, 28 August 2003 03:39:16 UTC