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RE: ISSUE-3: REPORTED: Lack of anonymous individuals

From: Conrad Bock <conrad.bock@nist.gov>
Date: Thu, 8 Nov 2007 11:16:52 -0500
To: "'Jim Hendler'" <hendler@cs.rpi.edu>, "'Boris Motik'" <boris.motik@comlab.ox.ac.uk>
Cc: "'OWL Working Group WG'" <public-owl-wg@w3.org>
Message-ID: <05c601c82222$c67d6c00$b3200681@MEL.NIST.GOV>

Boris,

 >  Let me give you a concrete example. Assume that O1 contains the  
 >  following ABox assertion:

 >  (13) hasParent(Bob,Mary)

 >  As long as O2 contains named individuals (Bob, Mary, and so on), you
 >  will get exactly the same answers. Now let O2 be an ontology
 >  containing the following ABox assertion:

 >  (14) hasParent(Bob,_:1)
 >  
 >  Here the difference becomes important. Under the standard "true"  
 >  semantics, O2 follows from O1. This is because, in first-order
 >  logic, hasParent(Bob,Mary) entails \exists x : hasParent(Bob,x).

So anonymous individuals translate to existentials?  I thought
anonymnous just meant "has no name".  Then O2 would only follow from O1
if sameAs(Mary, _:1).

 >  Under the approximative semantics, O2 *does not* follow from
 >  O1. This is because (14) is actually equivalent to the following
 >  ABox O2':

 >  (14) hasParent(Bob,some-invented-constant)

 >  Now in first-order logic, it is not the case that
 >  hasParent(Bob,Mary) entails hasParent(Bob,some-invented-constant),
 >  so O1 does not entail O2.

Though it would if =(Mary, some-invented-constant).

Conrad
Received on Thursday, 8 November 2007 16:17:41 GMT

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