From: pat hayes (phayes@ai.uwf.edu)
Date: 08/29/01
> > > > 1. What reason can there be to forbid subclass loops, other than > > subClassOf being understood to mean proper subclass? > >There is a modelling issue here, one that has very little to do with >semantics, and much more to do with pragmantics. Consider it in the same >class as forbidding incoherent class definitions. OK, I get the point (and Mike's related points). Indeed I wasn't thinking pragmatically :-) > > 2. Suppose Subclass is the subclass relation, Psubclass the > > proper-subclass relation, and R is any binary irreflexive relation > > between classes; then (R intersect Subclass) = (R intersect > > PSubclass). From which is follows that if some formal relation symbol > > on classes is loop-free, then if it can be interpreted as meaning > > subclass then it can also be interpreted as meaning proper subclass, > > without changing the truthvalues of any expressions in the language. > > So, what justification can there be for asserting that > > rdfs:subClassOf does *not* mean proper subclass? > >I don't see how this can be true. > >Suppose R is ``has a different ID than'', That is not an irreflexive relation on classes, since the same class may have two distinct IDs (ie two IDs may denote the same class.) > > Thanks for any input/feedback. As the RDFCore WG is on the very edge > > of adopting the model theory as a working draft, i would greatly > > appreciate any feedback asap, so we don't go public with a major bug. > >If RDF(S) was to exist in isolation then these issues would not matter >nearly so much. However, if RDF(S) is supposed to be *the* foundation for >the semantic web it *must* be amenable to extension, and issues such as >this have to be considered in the context of more-expressive formalisms. Right, point taken and I (now) agree. Pat --------------------------------------------------------------------- (650)859 6569 w (650)494 3973 h (until September) phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
This archive was generated by hypermail 2.1.4 : 04/02/02 EST