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Re: "OWL" Entailment

From: Ivan Herman <ivan@w3.org>
Date: Thu, 07 May 2009 11:45:50 +0200
Message-ID: <4A02ADCE.1060603@w3.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>
Thanks Bijan!

one small remark

Bijan Parsia wrote:
> 
> 2) If your data is contradictory, what should you return?
>     Typically, contractions entail everything, thus infinite answers.
>     Obvious solution is to return a fault (with no answers) and suggest
> using a weaker entailment regime.
> 

This may be dependent on the OWL Profile, too. The OWL RL (at least the
rule set) does not lead to infinite answers I believe. It does make
sense then to say that we return all possible answers. The issue is, of
course, how one signals that there _is_ a problem...

RDFS might be similar (disregarding the issue of infinite triple
generation with rdf:_n, but the approach in Herman ter Horst's paper
might take care of making that finite...)

(My mental model for using OWL RL and the 'finite' RDFS is that, before
the query, all possible extra triples are added to the graph and the
simple sparql query is done on that result. In this model it makes sense
to add all possible deductible triples to the triple store before the
query plus do something to signal a problem.)

Some interesting discussion ahead:-)

Cheers

Ivan

-- 

Ivan Herman, W3C Semantic Web Activity Lead
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Received on Thursday, 7 May 2009 09:46:27 GMT

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