From: <jos.deroo.jd@belgium.agfa.com>

Date: Tue, 10 Apr 2001 00:32:15 +0100

To: phayes@ai.uwf.edu

Cc: www-rdf-logic@w3.org

Message-Id: <OFA725E165.B4C80B30-ON41256A29.00811F15@bayer-ag.com>

Date: Tue, 10 Apr 2001 00:32:15 +0100

To: phayes@ai.uwf.edu

Cc: www-rdf-logic@w3.org

Message-Id: <OFA725E165.B4C80B30-ON41256A29.00811F15@bayer-ag.com>

> > > >When using resolution one cannot have such p->false rules. > > > > > > Incorrect. In fact, resolution REQUIRES the use of such clauses. > > > >Of course it requires the use of such clauses, but only ONE > >such clause, namely for the goal to be proved > > No, that is not correct. Resolution can be applied to any clauses. > Maybe some Prolog interpreters require there to be at most one > negated goal clause, but even Horn clause form doesnt state that > there must be only *one* negated clause. I had the resolution-as-implemented-by-prolog in mind and I apparently have to refresh my understanding of the original resolution algorithm of Robinson. [...] > > > >There is however an easier problem (maybe). > > > >On the proof level (where proof expressions live) > > > >we can discover that p has a no-proof-found value. > > > >Of course that is not the denial of p but that > > > >is not a problem for a proof expressions's life! > > > >All it has to express is evidence that can be > > > >syntactically checked to give semantic validity > > > >(and such expressions can contain p->false > > > >parts coming from negated premisses). > > > > > > I have no idea what you are talking about in the above paragraph. Can > > > you rephrase it? In particular, what is the 'proof level' ? > > > >The proof level is what TimBL has drawn so nicely in > >http://www.w3.org/2001/Talks/0228-tbl/slide5-0.html > > You really should not confuse a picture with a definition. I repeat, > what *is* the 'proof level'? For the moment I would say (but I'm sure others can do it much better) that proof-level is *the level where one deals with proofs* (level in the context of information system architecture) -- Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/Received on Monday, 9 April 2001 18:32:26 UTC

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