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Re: Expressiveness question

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Tue, 27 Jan 2004 11:14:31 +0000
Message-ID: <16406.18455.90672.402299@merlin.horrocks.net>
To: Sheila McIlraith <sheila@cs.toronto.edu>
Cc: pat hayes <phayes@ihmc.us>, www-rdf-rules@w3.org, daml-process@bbn.com

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 17:29:28 UTC

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