Re: Where DAML+OIL deviates from the RDF-Schema spec.

pat hayes wrote:
> >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.

Well, given the underlying idea that since we're on the
web we should assume that we can find more information,
when do we assume we ever know what all the Robin company
makes?  Of course, we know it doesn't make four sided triangles.

Received on Monday, 5 March 2001 23:39:03 UTC