- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Wed, 26 Sep 2001 10:04:11 -0500
- To: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
- Cc: www-rdf-rules@w3.org
> > The classical approach is to think of queries as negated >> and think of the entire inference process as finding a contradiction. >> That is a very 'logical' viewpoint which many find unnatural, > >It is not just unnatural but also not very general, because in >many formalisms/logics the principle underlying this approach, >viz proof by refuting the negation (or "reductio ad absurdum"), >is *not* valid! I wouldn't say 'many', myself. Even in weak logics which do not support the transformation as an inference, the 'negated' interpretation still has some utility. But your general point is well taken. >Although it is quite common to view the inference process >in logic programs in this unnatural way (apparently, because >many people like to be 'logical') We would all get along better if ad hominism were kept in check. The reason why I, and I suspect others, find this construction natural is not from some social need to impress people, but because it is sanctioned by the usual semantics for classical logic, and moreover pre-dates logical programming. >, there is absolutely no >need to do so. It is conceptually much more adequate (more >natural and more general) to view the inference process as >being based on simple rule application (detachment). This has its own problems and limitations, however. It confuses 'rule' in the sense of inference rule, with 'rule' in the sense of an implication; and, moreover, it obscures the underlying semantic unity between modus ponens and modus tollens inference forms (in classical logic, that is.) Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Wednesday, 26 September 2001 11:04:03 UTC