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RE: ISSUE-113 (OWL-R nonentailments): Some OWL-R nonentailments are OWL-Full entailments

From: Michael Schneider <schneid@fzi.de>
Date: Tue, 8 Apr 2008 10:16:05 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A0803D36@judith.fzi.de>
To: <public-owl-wg@w3.org>
Cc: <jjc@hpl.hp.com>
>ISSUE-113 (OWL-R nonentailments): Some OWL-R nonentailments 
>are OWL-Full entailments
>
>http://www.w3.org/2007/OWL/tracker/issues/
>
>Raised by: Jeremy Carroll
>On product: 
>
>
>Is a tool that provides all OWL-R rules and some others that 
>are licensed by OWL Full, still OWL-R conformant.
>
>i.e.
>
>if O1 entails O2 in OWL Full, but O2 does not follow using the 
>OWL-R ruleset applied to O1 then is an OWL-R conformant tool 
>permitted to find O2?

I would say "no".

Let's assume that O1 is consistent both under OWL-R and OWL-Full semantics. And let's further assume that it is possible in OWL-R to specify an NO2, which contradicts O2. An example might be:

    O2 := { u owl:differentFrom w }
    NO2 := { u owl:sameAs w }

Then the combined ontology O* := O1+NO2 will still be an R-consistent ontology. But O* will be Full-inconsistent, since the additional Full-entailment O2 contradicts NO2. 

Hence, with an "R+"-reasoner, which produces additional OWL R-non-entailments as inferences, it might become possible to create an ontology, which is R-consistent, but for which the "R+"-reasoner would tell me that this ontology is inconsistent. This is not what I would call "R-conformant behaviour". Generally, if a reasoner for a language L produces inferences for which there are no L-entailments, then this is what I know as "non-sound" L-reasoning.

So I would opt to say that an "OWL R-conformant" reasoner *MUST NOT* infer non-entailments of OWL R.

Cheers,
Michael

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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