- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Thu, 27 Sep 2001 20:15:33 -0500
- To: "Thomas B. Passin" <tpassin@home.com>
- Cc: www-rdf-logic@w3.org

>[Dan Connolly] >>[...] >> > Claim 3: >> > >> > For every basic untidy RDF graph R there is a core RDF interpretation >that >> > captures exactly the closure of the intended core RDF meaning of R and >that >> > is a model for R. That is, roughly, that there is a model that makes >> > everything implicitly (or explicitly) in the graph true, and everything >> > else false. >> >> I have no idea what the significance of this claim is, let >> alone any sense of whether I agree or disagree with it. >> > >I don't either, but it seems to bear on open versus closed systems. doesn't >it? Are there true statements not in the graph or not? There are certainly true statements not in any particular graph, sure. The fact that graph G has a canonical model doesn't imply that some larger graph G', which has G as a subgraph, might not itself have another, different, canonical model. That is the trouble with canonical models (closely related to closed worlds); they are very efficient, but very fragile. >Usually people say >(I think that includes you, right?) that the Web must be or is an open >system, while those interested in definitively proving things would like a >system to be closed. No!! The whole point, to me, of a 'classical' model theory is that the notion of entailment that it supports refers to ALL interpretations, which has the consequence that if G entails F, then it goes on entailing it even if it gets bigger, ie any G' containing G also must entail F. ANY G', even the entire Web. Entailment supports a notion of proof which is as definitive as you could hope for, and absolutely does not require any closed-world assumptions. > Perhaps this gives you a way to construct a closed >system if you need one. The problem is not constructing them when you need to, but what to do with the conclusions you draw when you have constructed one. They are only valid inside that closed world; if let loose, naked, in a wider world they cannot be relied upon. Pat Hayes -- --------------------------------------------------------------------- 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 Thursday, 27 September 2001 21:15:37 UTC