- From: tim finin <finin@cs.umbc.edu>
- Date: Fri, 05 Oct 2001 10:33:26 -0400
- To: www-rdf-rules@w3.org
- CC: Drew McDermott <drew.mcdermott@yale.edu>
Drew McDermott wrote: > ... > > Can someone give me a test case which shows where the difference is? > ... > The simplest case is this one: If P->Q is an implication, then it > enables you to infer not-P from not-Q. If it is an inference rule, it > allows you to infer Q from P, period. > ... > Gerd provided a lot of useful examples as well, although perhaps he > too faithfully obeyed the principle of latino gullibilum impressis. I always liked the example that was given in the KIF documentation (KIF 3.0 Ref. Manual, http://logic.stanford.edu/kif/Hypertext/node37.html): "The rationale for using monotonic rules in knowledge representation, instead of implications, is twofold. On the one hand, the ``directed'' character of rules can simplify the task of developing efficient inference procedures. On the other hand, in some cases, replacing <<= by <= would be semantically unacceptable. For instance, the rules (<<= (status-known ?x) (citizen ?x)) (<<= (status-known ?x) (not (citizen ?x))) allow us to infer (status-known Joe) only if one of the sentences (citizen Joe), (not (citizen Joe)) can be inferred. Replacing the rules by implications would make (status-known ?x) identically true."
Received on Friday, 5 October 2001 10:23:43 UTC