- From: pat hayes <phayes@ai.uwf.edu>
- Date: Wed, 18 Sep 2002 16:01:04 -0500
- To: w3c-rdfcore-wg@w3.org
Guys, Recent attempts (in collaboration with Peter and Ian) to reconcile the RDF(S) MT with the emerging OWL MT have suggested that it would be good to make a technical alteration to the semantic conditions for RDFS. I think that this change will make no appreciable difference to RDFS itself (ie it will give the same RDFS entailments), but am soliciting comments on this change from the WG before deciding to do it. We can illustrate the point by considering rdfs:subClassOf. Right now, we say that A rdfs:subClassOf B is true in I if ICEXT(I(A)) is a subset of ICEXT(I(B)). Which seems kind of obvious; but the idea is to change this to read " ... is true in I IFF ... " , i.e. make the semantic conditions *necessary and sufficient* for the truth of the triple. The reason this doesnt make any appreciable difference to RDFS is that RDFS has no notion of negation, so it doesnt really matter if it treats something as false when its really true, which would be possible in the current MT: that is, you could (currently) have two classes and one class extension be a subset of the other, and still count rdfs:SubClassOf as being false in that interpretation. That wouldnt matter since that interpretation wouldnt satisfy any antecedents that might trigger a wierd conclusion, since it just fails to make something true. But when we go to OWL, there is something like a negation (owl:complementOf), and so now this possible mismatch between what is actually correct in the interpretation and what triples the interpretation makes true suddenly starts to matter, both ways round. Similar changes need to be made to the conditions for rdfs:subPropertyOf and the domain and range conditions, for similar reasons. Unless anyone objects, I plan to make this change in the next (and hopefully close-to-final) version. So object now or forever hold your piece. (To emphasize, this change makes the MT *more* conventional rather than less, ie this is the standard way to do it) Pat -- --------------------------------------------------------------------- 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 Wednesday, 18 September 2002 17:01:07 UTC