- From: patrick hayes <phayes@ai.uwf.edu>
- Date: Fri, 14 Jun 2002 22:02:20 -0500
- To: Dan Connolly <connolly@w3.org>
- Cc: w3c-rdfcore-wg@w3.org
>On Fri, 2002-06-14 at 10:37, R.V.Guha wrote: >> As for not using the rule of the excluded middle, etc. --- This is a >> much bigger issue than axiomatic approaches vs model theoretic >> approaches. The current model theories, from webont & rdf, do assume >> the law of the excluded middle. > >WebOnt does, yes. But RDF's model theory doesn't have negation >at all... but... hmm... I suppose it does say that every >triple (and every graph) is either true or false in >every interpretation. Hmmm... I wish you hadn't pointed >that out; I wasn't worried about it before now. ;-) OK, let me suggest that you worry less. As you say, RDF has no negation. OK, so take a 2-valued interpretation, and re-interpret it so that 'false' means something else, eg 'not known to be true' or 'false or undefined' or whatever takes your fancy as long as it definitely does not overlap with 'true'. Since entailment refers to satisfaction, which refers to truth, and there is no negation, what we call the 'not-true' value for propositions isn't really germane to the MT at all. You could interpret RDF intuitionistically or like LCF (truthvalues are true and undefined) and it would have exactly the same entailments. Of course, this doesn't extend to anything that has even a smidgeon of negation in it, such as DAML or OWL. But if you stay strictly in RDF, nobody can force you to exclude your middle. Pat -- --------------------------------------------------------------------- IHMC (850)322 0319 cell 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax
Received on Friday, 14 June 2002 23:02:20 UTC