- From: pat hayes <phayes@ai.uwf.edu>
- Date: Mon, 23 Sep 2002 21:17:48 -0500
- To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
- Cc: www-webont-wg@w3.org
>[...] > >> >> BTW, strengthening domain and range to IFF seems to me to be a really >> >> bad idea, in general: it completely destroys the idea of conjunctive >> >> range/domain assertions. We put the current semantics into RDFS in >> >> order to conform to the DAML conjunctive semantics, so why do you >> >> want to blow this out of the water in OWL? >> > >> >I don't understand why you are saying this? How does making domain and >> >range IFF destroy the conjunctive semantics? >> >> Because if superclasses of ranges are also ranges, then there is no >> information to be gained by asserting more about a range. All >> properties range over the universe. The whole point of allowing >> conjunctive semantics on ranges is so that one can accumulate >> information that allows one to pin down a range more precisely. > >Huh? > >If I say > >A: > ex:bar rdfs:subClassOf ex:baa . > ex:baz rdfs:subClassOf ex:bar . > ex:foo rdfs:range ex:bar . > >Then no matter whether ex:foo has an IFF reading or an ONLY IF reading >any object of an ex:foo triple must belong to both ex:bar and ex:baa >so > >B: > ex:bar rdfs:subClassOf ex:baa . > ex:baz rdfs:subClassOf ex:bar . > ex:foo rdfs:range ex:bar . > ex:a ex:foo ex:b . > >RDFS entails > > ex:b rdf:type ex:bar . > ex:b rdf:type ex:baa . Right, of course. Whch is why Jeremy's entailment is beside the point. >The only difference is that under an IFF reading graph A RDFS entails > > ex:foo rdfs:range ex:baa . Right, and I don't think it should. Here's an analogy. If I'm in my house, then I'm in Pensacola. I live in Pensacola, true: but it would be a mistake to infer that my house *was* Pensacola. > >If I say instead > >C: > ex:bar rdfs:subClassOf ex:baa . > ex:baz rdfs:subClassOf ex:bar . > ex:foo rdfs:range ex:bar . > ex:foo rdfs:range ex:baz . > >then more information has definitely been gained, as C RDFS entails > > ex:foo rdfs:range ex:baz . > >which was not an RDFS entailment of A. Well, yes. But on your semantics that doesn't tell me very much, since ex:foo rdfs:range rdf:Resource . no matter what you tell me, so I can't use any of these range assertions to localise the range more exactly. If all we were inferring was rdf:type assertions then it wouldnt matter much, but ranges are used for more than that. You have suggested attaching datatyping information to ranges, for example; if all properties have the universe as a range then this becomes impossible. > >Further > >D: > ex:bar rdfs:subClassOf ex:baa . > ex:baz rdfs:subClassOf ex:bar . > ex:foo rdfs:range ex:bar . > ex:foo rdfs:range ex:baz . > ex:a ex:foo ex:b . > >entails > > ex:b rdf:type ex:baz . > >which is not an RDFS entailment of B. Yes, but this is true under either interpretation of range, right? I fail to see what point you are making here. Pat (rest of response on another thread) -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Monday, 23 September 2002 22:17:42 UTC