- From: Michael Kifer <kifer@cs.sunysb.edu>
- Date: Mon, 29 Aug 2005 11:11:40 -0400
- To: "Gerd Wagner" <wagnerg@tu-cottbus.de>
- Cc: public-rule-workshop-discuss@w3.org, analyti@ics.forth.gr, "'Carlos Viegas Damasio'" <cd@di.fct.unl.pt>, antoniou@ics.forth.gr
Gerd, Yes, it is a weaker kind of negation. My point is that it doesn't use NAF and is suitable for cases like the pharmacy example in the charter where you might not want to jump to conclusions. --michael > > By the way, we are not advocating for NAF at the exclusion of > > classical negation. There are extensions of LP, which support > > classical negation as well (flora-2 doesn't support that yet). > > That's not quite true, Michael: the second negation (e.g. in > extended logic programs as defined by Gelfond and Lifschitz) is > only called "classical", but it is not clasical negation because > it does not obey the law of the excluded middle (LEM). And this > should not come as a surprise: the LEM creates a certain kind of > indefiniteness (e.g. it implies the principle of reasoning by > cases) that cannot be handled by a computational system without > severe restrictions (such as DL). > > Therefore the second negation in these formalisms does not > correspond to classical 2-valued (i.e. Boolean) negation, but > rather to 3/4-valued Kleene negation. > > These 2 negations are also available in RuleML. Notice > also that there is an ISWC'05 paper about extending RDF by > adding these 2 negations (NAF and Kleene-NEG) to it [1]. > > -Gerd > > [1] A. Analyti, G. Antoniou1, C. V. Damasio and G. Wagner: > Stable Model Theory for Extended RDF Ontologies > http://www.informatik.tu-cottbus.de/~gwagner/REWERSE-I1/ERDF-ISWC-05.pdf > > > -------------------------------------------- > Professor Gerd Wagner > http://www.informatik.tu-cottbus.de/~gwagner > Email: G.Wagner@tu-cottbus.de > Tel: (+49 355) 69 2397 > Institute of Informatics > Brandenburg University of Technology > at Cottbus, Germany > > > >
Received on Monday, 29 August 2005 15:12:07 UTC