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Re: Expressiveness question

From: Sheila McIlraith <sheila@cs.toronto.edu>
Date: Tue, 27 Jan 2004 11:39:51 -0500
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: pat hayes <phayes@ihmc.us>, www-rdf-rules@w3.org, daml-process@bbn.com
Message-ID: <Pine.GSO.4.58.0401271135160.6276@dvp.cs>


Ian,

This is very helpful and interesting.  <Though I need to work through
an example in more details to understand all of the implications.>

Regarding the question of whether the disjunctive literals in FOL would be
encoded as classes or properties in OWL, my sense is that actions (e.g.,
a=pickup(x)) would be encoded as classes.  I'll think about whether
fluents in the situation calculus (predicates, indexed by the situation
term, whose truth value can changes as a result of an action) could be
encoded as classes as well.

Sheila



On Tue, 27 Jan 2004, Ian Horrocks wrote:

> On January 25, Sheila McIlraith writes:
> >
> >
> > Hi Pat,
> >
> >
> > On Tue, 20 Jan 2004, pat hayes wrote:
> >
>
> [...]
>
> > > holding(x, do(a,s)) IMPLIES ((a=pickup(x)) OR (holding(x,s) )
> > >
> > > isn't, and isn't ever likely to be stateable in any rule language.
>
> But given that in SWRL combines rules with OWL, we get something much
> more powerful which may allow us to state more that in normal rule
> languages. E.g., if the disjunction in the head of the rule included a
> unary predicate:
>
> Body IMPLIES P1(x) OR P2(x)
>
> then we would be able to state it in SWRL because we can rewrite it as
>
> Body AND NOT P2(x) IMPLIES P1(x)
>
> SWRL allows us to use (NOT P2) as a predicate (or we could use OWL to
> assert that the class NOT-P2 as equivalent to the negation of the
> class P2).
>
> Whether or not this kind of trick would work for the rule Pat wrote
> would depend on how (a=pickup(x)) and (holding(x,s)) are encoded: if
> they are encoded as binary predicates (OWL properties), then it seems
> unlikely that we can express it in SWRL as it would amount to
> providing property negation, and Uli Sattler has managed to convince
> me that we (almost certainly) can't express property negation in SWRL.
>
> Regards,
>
> Ian
>
Received on Tuesday, 27 January 2004 15:21:39 UTC

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