- From: Dan Connolly <connolly@w3.org>
- Date: Wed, 22 Nov 2000 22:00:37 -0600
- To: Ian Horrocks <horrocks@cs.man.ac.uk>, www-rdf-logic@w3.org
Dan Connolly wrote:
>
> Ian Horrocks wrote:
> [...]
> > The DAML-OIL proposal can be found at:
> >
> > http://www.cs.man.ac.uk/~horrocks/DAML-OIL
> This one seems broken:
>
> #3. The semantics of restrictions has been changed...
>
> I'll explain why in a separate message.
Hmm... I take it back. I got the impression that the
sematnics of restrictions was based on the XML syntax,
which, at the RDF graph level, looks like using
negation-as-failure.
But now that I look closely at the semantics, I see
it's specified in RDF terms, i.e. in triples:
| <type,?R,Restriction> <onProperty,?R,?P> <toClass,?R,?C>
| x in IC(?R) iff IR(?P)({x}) <= IC(?C)
|
| <type,?R,Restriction> <onProperty,?R,?P> <toValue,?R,?V>
| x in IC(?R) iff <x,IO(?V)> in IR(?P)
Let me check my understanding with an example...
let's say a Square is a RegularPolyhedron
with numberOfSides=4:
<subClassOf,Square,RegularPolyhedron>
<type,Square,Restriction> <onProperty,Square,numberOfSides>
<toValue,Square,4>
means
x in IC(Square) iff <x,4> in IR(numberOfSides)
oops... no, that's not right... rather:
<intersectionOf,Square,[RegularPolyhedron, FourSidedThing]>
<type,FourSidedThing,Restriction>
<onProperty,FourSidedThing,numberOfSides>
<toValue,FourSidedThing,4>
which will end up with
x in IC(FourSidedThing) iff <x,4> in IR(numberOfSides)
and
x in IC(Square) iff x in IC(FourSidedThing)
and x in IC(RegularPolyhedron)
Yes, that works.
I'm still not certain there are no closed-world assumptions...
I'll try to study the semantics some more. But the problem
that I initially thought was there isn't.
--
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 22 November 2000 23:00:45 UTC