- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Tue, 21 May 2002 14:18:17 -0400
- To: jos.deroo.jd@belgium.agfa.com
- Cc: www-webont-wg@w3.org
From: "Jos De_Roo" <jos.deroo.jd@belgium.agfa.com> Subject: Re: ISSUE: DAML+OIL semantics is too weak Date: Mon, 20 May 2002 23:16:12 +0200 [...] > > How is modus tollens unsafe? > > I think the trouble starts with your rule > ?x a ?y, ?x a [owl:complementOf :y] -> FALSE > > We can't assert such a rule with a conclusion > that is FALSE (as it is not a Horn clause). It is a Horn clause, just not a definite clause, as you yourself have admitted. | From: jos.deroo.jd@belgium.agfa.com | To: pfps@research.bell-labs.com | Cc: sandro@w3.org, phayes@ai.uwf.edu, www-rdf-logic@w3.org | Date: Tue, 30 Apr 2002 21:47:27 +0200 | Message-Id: <OFCBB60AED.53261F74-ONC1256BAB.00686C6E@bayer-ag.com> | | [...] | | PS indeed a Horn clause is a disjunction with at most one positive literal | but we never assert clauses with no positive literal (which is a query) I'm not responsible for the problems that you are getting yourself into by only allowing definite clauses. I don't have any problems with rules of inference like modus tolens. If you have problems with modus tolens perhaps the problems are not with modus tolens but with your system. > We would rather write a rule like > { :rule16c1 . ?x a ?y . ?x a ?z . ?y owl:complementOf ?z } > log:implies { ?x :inconsistentWith owl:complementOf } . > > so have the inconsistency detected explicitly > and that would not mean discharging assumptions. I am unsure as to whether an approach like this would be viable. peter
Received on Tuesday, 21 May 2002 14:18:28 UTC