- From: pat hayes <phayes@ai.uwf.edu>
- Date: Mon, 5 Mar 2001 22:32:22 -0600
- To: tim finin <finin@cs.umbc.edu>
- Cc: Tim Berners-Lee <timbl@w3.org>, "Sigfrid Lundberg, Lub NetLab" <siglun@gungner.lub.lu.se>, Peter Crowther <Peter.Crowther@melandra.com>, www-rdf-logic@w3.org
>Tim Berners-Lee wrote: > > I think we all agree that < and <= style of subProperty are both >consistent > > reasonable terms. > > ... > > 1. Saying that subclassOf(c,d) is a way of saying forall x, in(x,c) => > > in(x,d) which is a simple thing to say. Lots of rules systems >allow that to be > > expressed. > > > > Saying properSubClassOf(c,d) is to say > > forall x. in(x,c) => in(x,d) and exists y. in(x,d) and not(in(x,c)) > > This is a more complicated thing to say, as it uses a "not". > >If we take c and d to be intensional descriptions then wouldn't it >be better to say that it means possible((Ey) in(y,d)^not(in(y,c)))? The >car example would then be ok as long as it was logically possible for >the Robin company to make something with other than three wheels. God forbid that we take these to be intensional. We've only just got an extensional semantics straight; if we have to incorporate modalities we will never recover. But in any case, DAML+OIL is an inherently extensional language in the mold of CLASSIC: it refers to classes. To illustrate the snags, Tim, let me ask you to elucidate just what it would mean for it to be logically impossible for a company to make anything? It is *logically* possible that the Robin company might make, say, statues of the Buddha the size of a planet constructed entirely from icecream. 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 Monday, 5 March 2001 23:30:53 UTC