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Re: [RDF+OWL] impossible to coreify OWL 2 RL combinations

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Mon, 02 Feb 2009 18:54:39 +0100
Message-ID: <4987335F.5040007@inf.unibz.it>
To: RIF WG <public-rif-wg@w3.org>

Jos de Bruijn wrote:
> It is impossible to completely coreify the embedding of OWL 2 RL
> combinations, because there is equality in that language.  A na´ve
> axiomatization such as use of sameAs (as in [1]) is not sufficient,
> because in combinations one can use arbitrary predicates.
> For example, if the ontology says:
> FunctionalProperty(p)
> ClassAssertion(C a)
> PropertyAssertion(p e a)
> PropertyAssertion(p e b)
> With the na´ve sameAs axiomatization we can derive
> a[sameAs -> b] and b[rdf:type -> C]
> However, if we add the RIF fact
> q(a)
> we cannot derive q(b) unless we have a full-blown axiomatization of
> equality (which is doable because there are no function symbols in
> Core).  This would, however, clearly defeat the purpose of not having
> equality in Core.
> So, either (a) we say that you effectively leave Core when going for OWL
> 2 RL or (b) we provide an embedding of an equality-free subset.
> I would be in favor of (a), because I do not want to define yet another
> OWL subset; I think the whole web of semantic Web languages is already
> complicated enough.
> Best, Jos

Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
No one who cannot rejoice in the discovery of
his own mistakes deserves to be called a
  - Donald Foster

Received on Monday, 2 February 2009 17:54:48 UTC

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