- From: Jos De_Roo <jos.deroo@agfa.com>
- Date: Sat, 5 Apr 2003 20:42:19 +0200
- To: geoff@sover.net
- Cc: www-archive@w3.org
Yes Geoff, that very much does seem like a reasonable approach. Modulo renaming, all exi-vars in the body do become uni-vars within the scope of the rule body => head, so that could help as well I think. Wrt to comprehension, I'm still thinking that there is an alternative for Skolem functions, but I haven't found it yet... -- , Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/ "Geoff Chappell" To: Jos De_Roo/AMDUS/MOR/Agfa-NV/BE/BAYER@AGFA <geoff@sover.n cc: <www-archive@w3.org> et> Subject: RE: RDF and OWL rules 2003-04-05 08:20 PM Hi Jos, > -----Original Message----- > From: Jos De_Roo [mailto:jos.deroo@agfa.com] > Sent: Friday, April 04, 2003 6:49 PM > To: geoff@sover.net > Cc: www-archive@w3.org > Subject: RE: RDF and OWL rules > > [...] > > I wonder if an initial target of supporting lite-like cardinalities (0, > > 1, >1) might be a good idea for this reason. > > indeed, we also like "first doing the simple things" On this note, I've been looking at breaking down the rules into the following groups: - rules arising from "if" semantics of vocabulary items (we should be able to capture all of these. I think these are the ones that can be expressed with all universally quantified variables in the head, and all other body variables existential - a natural fit for LP languages) - rules arising from "iff" semantics of vocabulary items (we can do some of these. I think these amount to the rules with all universally quantified variables in the head, but also some of the body variables are universally quantified. I imagine we can only capture those that allow us to evaluate a forall in the body without making a closed world assumption) - rules arising from comprehension principles (we can do some of these - I think these are the ones that have some existentially quantified variables in the head requiring a skolem function of some sort; much danger of infinite generation here) I've been categorizing the different rules along those lines (I'll send you those when I'm done). I'm thinking that we ought to be able to close off the first group pretty easily - we just make sure we have a rule that expresses the if conditions of each vocabulary item (we probably have all of those rules already) For the second and third groups, I want to try to further characterize the ones that we can capture and the ones that we can't. Hopefully based upon that characterization, we can't be sure that we've gotten all of the ones we can. Does that seem like a reasonable approach to you? Regards, Geoff [1] http://www.w3.org/TR/2003/WD-owl-semantics-20030331/rdfs.html
Received on Saturday, 5 April 2003 13:42:33 UTC