- From: Christian de Sainte Marie <csma@ilog.fr>
- Date: Thu, 01 Sep 2005 11:06:35 +0200
- To: Michael Kifer <kifer@cs.sunysb.edu>
- CC: public-rule-workshop-discuss@w3.org
Michael Kifer wrote: > > Inference rule is a useful way to think of it at an intuitive level. > However, the only version of CWA that is defined as an inference rule that > I know of is NAF. Not what is being called NAF in this discussion thread, > but the real NAF, as in Prolog. > > All the other popular versions of CWA (well-founded, stable, > circumscription) use model-theoretic definitions or axiomatic. I stand corrected: I had Clark's NAF in mind. > Then you are checking whether S3 still entails F, and sure enough it does. > So, you conclude it is monotonic. Point taken: I tried so hard to hide the assert that I did not notice it myself! > But here you have "monotonicity" for > formulas of a certain kind (the same problem as Dan had), not for all > formulas. As far as I recall, according to so called Gabbay's postulates, > *every* *non*monotonic logic also has the property that if S |= F then > S+F+something |= F. > In any case, the most popular CWA flavors (the well-founded and stable > models) do have the above property. > So, your argument in the use case doesn't establish anything as far as > monotonicity goes. I fear that it had more to do with the ostrich's postulate than Gabbay's. Something like: S |= F, but S + B |\= F? No problem: just ignore B! (What do you tell me, S |= F is non-monotonic nonetheless?) What? Me? Foolish? > What we should do is to remove the clause that NAF is out of scope and > remove the reference to monotonicity. Then let the WG deal with it. I could leave with that, but for the fear of that being Pandora's box... Christian
Received on Thursday, 1 September 2005 09:05:33 UTC