- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Tue, 16 Apr 2002 19:22:41 -0400
- To: Steven Gollery <sgollery@cadrc.calpoly.edu>
- Cc: www-rdf-logic@w3.org
>Pat, > >I don't have the background to discuss most of the fallacies you >mention , but I >would like to talk about one of them: > >Pat Hayes wrote: > >> 21. The fact that rdfs:Resource is both an instance and a superclass >> of rdfs:Class is a "problem". > >One of the things I was working on when I started looking at RDF and >DAML was to be >able to generate RDF/DAML from UML system models. I thought it might >be useful to >consider RDF and DAML from a metamodeling perspective, so that there was a >correspondence to OMG's layered metamodeling architecture. Then I >could translate >from the MOF in the XMI representation of the UML model, to an >equivalent set of >instances of an RDF metamodel. > >But my effort foundered on points exactly like the one you mention: the way I >understand layered metamodel architectures, for "class A" to be an instance of >"class B", B must be on a higher metamodel layer than A. But for >class A to be a >superclass of class B, both classes must be on the same layer. This >is true in the >metamodeling world, but apparently not a consideration in the RDF world. RDF does not impose layering. But I don't quite see why your effort foundered. Nothing in the RDF world *prevents* you from imposing such a layered view of the world, if you wish to do so. (You could define a notion of uml:subClassOf, uml:Instance, and so on, which would be subProperties of the corresponding rdf: or rdfs: properties, and so could have more restrictive conditions. To ensure metamodel layering, you could impose appropriate range and domain conditions. ) The UML kind of view is not incompatible with RDF, but RDF allows other perspectives to exist as well. So even if you wish to work from such a limited, constraining and arbitrary perspective as that used by OMG (sorry, but I couldn't resist), RDF does not prevent you doing so. So I see no 'problem' here, unless of course you (like, apparently, Pan and Horrocks) believe that the entire world should be restricted to your (or, better, OMG's) narrow perspective. >So whether this is a problem or not depends on what we're trying to >accomplish. >Which is true of everything, I suppose. Indeed. 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 Tuesday, 16 April 2002 19:22:44 UTC