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Re: Proposed revision to daml-ont

From: Dan Connolly <connolly@w3.org>
Date: Wed, 22 Nov 2000 22:00:37 -0600
Message-ID: <3A1C9665.2F50C2D9@w3.org>
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

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