From: Michael Kifer <kifer@cs.sunysb.edu>

Date: Fri, 26 Aug 2005 12:27:27 -0400

To: jos.deroo@agfa.com

Cc: dieter.fensel@deri.org, Christian de Sainte Marie <csma@ilog.fr>, public-rule-workshop-discuss@w3.org

Message-Id: <20050826162727.EBC2CCB5DB@kiferserv.kiferhome.com>

Date: Fri, 26 Aug 2005 12:27:27 -0400

To: jos.deroo@agfa.com

Cc: dieter.fensel@deri.org, Christian de Sainte Marie <csma@ilog.fr>, public-rule-workshop-discuss@w3.org

Message-Id: <20050826162727.EBC2CCB5DB@kiferserv.kiferhome.com>

> > very helpful Dieter; thanks > [...] > > "Assume you have > > > > p(a,b), p(b,c) > > and the following two rules: > > p(x,y) -> q(x,y) > > p(x,y) & p(y,z) -> q(x,z) > > > > Then under minimal model semantics q is the deductive > closure > > of p, i.e., q(a,b), q(b,c), q(a,c) are true and no other > q(x,y) us true. > > In FOL, this is different since you cannot exclude models > in which > > q(a,a) is true. That is, you cannot express deductive > closure in FOL." [1] > > what if (somewhere on the web) it is also the case that > a owl:sameAs b > (it was first order notation with equality) This is why, in order to make NAF well-defined, the scope of the inference must be also well-defined. This is where SNAF comes in. In NAF, the scope is implicit, but well-defined. However, this implicitness doesn't work well on the web because the Web is practically infinite. There is always that "somewhere on the web" as you put it, which the engine may not be aware of. One way out of this is to let the user specify the scope of the inference explicitly (which is what SNAF really is). In this way, you tell the engine where to look. --michaelReceived on Friday, 26 August 2005 16:58:51 UTC

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