- From: Gerd Wagner <wagnerg@tu-cottbus.de>
- Date: Mon, 29 Aug 2005 11:00:29 +0200
- To: "'Michael Kifer'" <kifer@cs.sunysb.edu>
- Cc: <public-rule-workshop-discuss@w3.org>, <analyti@ics.forth.gr>, 'Carlos Viegas Damasio' <cd@di.fct.unl.pt>, <antoniou@ics.forth.gr>
> 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 09:02:08 UTC