- From: Sigfrid Lundberg, Lub NetLab <siglun@gungner.lub.lu.se>
- Date: Fri, 11 May 2001 13:39:25 +0200 (MET DST)
- To: pat hayes <phayes@ai.uwf.edu>
- cc: "Sean B. Palmer" <sean@mysterylights.com>, www-rdf-logic@w3.org
On Thu, 10 May 2001, pat hayes wrote: ... > The issue is being able to infer equivalence from other assertions. > > >In other > >words, if someone can come up with an practical real world example of > >why cyclic classes should be introduced over equivalence (or why > >cyclicity is required for equivalence... in Notation3!), then I would > >be very glad to hear it. > > Nobody (except you) is talking about these 'cyclic classes', whatever > they are. We are all talking about classes. > > Pat Hayes > > PS. You know, this little exchange is a lovely illustration of the > utility of a formal semantics. "Subclass" sounds like it means > something, but exactly what it means needs to be spelled out in > mathematical terms to avoid needless misunderstanding. I think that the problem here boils down to the wish to be able to say things, and the wish to be able to infer things. I want to be able to say that a sub-title is a subclassof title, and that there should be no doubt whatsoever that all titles are not sub-titles. Just some titles are. Some time ago, I was convinced by you (and other kind people on this list) that we do need a not-strict-sub-class-of. The cost of making certain inferences be would far too high if we didn't. So I accept this... But I'm not comfortable with it; aren't we trading inferability against expressiveness? Aren't we enhancing the former at the price of the latter. To put this in another way: Could the ability to say (i.e., in rdf/daml) that sub-titles "<" titles rather than just that sub-titles "<=" titles make a more solid ground for inference. I mean, some statements could actually be more precise... I'd reckon that we need both. Sigge
Received on Friday, 11 May 2001 07:29:18 UTC