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Re: Sketch: reasoning conformance levels

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 07 Nov 2002 11:38:30 -0500 (EST)
Message-Id: <20021107.113830.32963939.pfps@research.bell-labs.com>
To: welty@us.ibm.com
Cc: www-webont-wg@w3.org

From: Christopher Welty <welty@us.ibm.com>
Subject: Re: Sketch: reasoning conformance levels (was RE: Issue: Add hasValue to OWL Lite)
Date: Thu, 7 Nov 2002 11:23:03 -0500

> 
> I don't think there is any reason to say OWL Full is not for reasoners, 
> nor have I seen any evidence to date that OWL Full is incomplete, though 
> I've noticed several messages that seem to take it for granted.  

Well, it doesn't make much sense to describe a semantics as incomplete in
this context, and, in any case, I think that the OWL/Full semantics is no
different from the OWL/DL semantics in this respect.

> In fact, 
> I believe OWL Full is sound and complete, though intractable as all hell 
> I'm sure. 

More accurately, entailment in OWL/Full is (likely) undecidable and not
amenable to complete implementation by DL reasoners.  (I seem
to remember arguments, perhaps even by me, that it *is* undecidable.)  

> Therefore I believe the only thing we can say about OWL Full, wrt 
> reasoning and reasoners, is that no one knows how to build a reasoner that 
> supports all of OWL Full.

Actually, it should be possible to build a complete (one-sided) reasoner
for OWL/Full as entailment in OWL/Full is semi-decidable.  Just axiomatize
in SKIF and then axiomatize the resulting SKIF in standard FOL and use a
complete FOL reasoner.  I don't expect to see blazing performance, however,
:-)

> Dr. Christopher A. Welty, Knowledge Structures Group
> IBM Watson Research Center, 19 Skyline Dr.
> Hawthorne, NY  10532     USA 
> Voice: +1 914.784.7055,  IBM T/L: 863.7055
> Fax: +1 914.784.6078, Email: welty@us.ibm.com

peter
Received on Thursday, 7 November 2002 11:38:51 GMT

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