- From: pat hayes <phayes@ai.uwf.edu>
- Date: Wed, 30 May 2001 21:02:43 -0500
- To: Sergey Melnik <melnik@db.stanford.edu>
- Cc: pfps@research.bell-labs.com, www-rdf-logic@w3.org
>"Peter F. Patel-Schneider" wrote: > > > > In defense of stripped-down RDF, there is nothing technically wrong with a > > logical formalism that can represent only positive ground triples. Such a > > formalism can certainly convey some useful semantic information. > > > > It is just that such a representation formalism cannot be used to > > *represent* anything more than positive ground triples. Using positive > > ground triples to encode a more-expressive formalism requires >encoding, which > > requires a new semantics, defined on top of the semantics for the positive > > ground triples, and makes it essentially impossible to use the semantics > > for the positive ground triples to represent domain information. > >Is that true indeed? If a logical formula is encoded as a set of >statements, ?? A logical formula IS a statement. (Do you mean as a set of RDF 'facts'?) What do you mean here by 'encoded as' ? (Not just quibbling, I really am not sure what you take this to mean, and I think it is central to get this clear, as different senses of 'encoding' would give different answers.) > wouldn't it be possible to find an interpretation that maps >the corresponding resources into the domain of discourse, which contains >people, Web sites, logical formulae and classes? Interpretations (in the logical sense: if you meant some other sense then I do not follow you exactly) map expressions into semantic values (of various kinds, depending on the syntactic category of the expression). So in order to even define an interpretation in this sense, one needs to connect it to the logical syntax. The issue now is, what IS the logical syntax of an expression 'encoded' into RDF? I think Peter's point is that the logical syntax cannot actually be the RDF syntax if the logic is anything more expressive than positive ground triples. I am not quite sure what you mean by an interpretation that maps resources to something. As I understand it, resources *are* the semantic values, ie the things in the domain of discourse; but those are not usually thought of as including logical formulae (or at any rate, if logical formulae are in the domain of discourse, those are not usually the same expressions that are being interpreted at the time.) >Wrt the latter: it is absolutely necessary to map resources that >represent classes onto sets of objects in the domain of discourse (D)? >Would it be possible to map such resources to elements of D that >represent classes and have certain relationships with their members? Peter may have a different answer, but I would say that these amount to the same thing. The second case puts the classes (=sets) themselves into the domain as well as their members, which is OK. It is an option, at any rate. 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 Wednesday, 30 May 2001 22:02:47 UTC