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Re: Question on DL negation

From: Michael Schneider <m_schnei@gmx.de>
Date: Wed, 07 Mar 2007 23:10:17 +0100
Message-ID: <45EF3849.3000702@gmx.de>
To: pratt@cs.stanford.edu
CC: semantic-web@w3.org, public-owl-dev@w3.org, bparsia@cs.man.ac.uk

Vaughan Pratt wrote on Wed, 07 Mar 2007:
> Bijan Parsia wrote:
>> Well, disjointness is *weaker* than full negation. For example, in OWL, 
>> A disjointWith B is just syntactic sugar for A subclassof complementOf(B).
> 
> Are there technical (e.g. computational complexity) benefits to this 
> definition over the more usual (and more constructive) definition in 
> terms of emptiness of intersectionOf(A,B)?

Thanks, Vaughan!

That's an even more obvious example, how one can simulate a disjointness 
axiom between two classes A and B within OWL-/Lite/. Restated:

   EquivalentClasses(owl:Nothing intersectionOf(A B))

'owl:intersectionOf' is explictly allowed vocabulary within OWL-Lite, as 
long as the classes mentioned are named classes (or restrictions), see

   http://www.w3.org/TR/2004/REC-owl-features-20040210/#intersectionOf

Bijan's 'complementOf' construction only works in OWL-DL, where 
'owl:disjointWith' is given anyway. (But to be fair, keeping within 
OWL-Lite wasn't the topic in Bijan's cited explanation - this first came 
up in a later mail).

Cheers,
Michael
Received on Wednesday, 7 March 2007 22:10:30 GMT

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