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Re: ISSUE: DAML+OIL semantics is too weak

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 20 May 2002 11:15:29 -0400
To: phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org
Message-Id: <20020520111529C.pfps@research.bell-labs.com>
From: patrick hayes <phayes@ai.uwf.edu>
Subject: Re: ISSUE: DAML+OIL semantics is too weak
Date: Sun, 19 May 2002 00:52:45 -0500

> >TITLE:       DAML+OIL semantics is too weak
> >DESCRIPTION: DAML+OIL semantics (both the model theory and the
> >	     axiomatization) are too weak.  For example, it does not allow
> >	     the inference of membership in any restrictions that are not
> >	     present in the knowledge base, even though many of these are
> >	     desirable consequences.   For example, if John is an instance
> >	     of both Person and Employee, DAML+OIL does not sanction the
> >	     conclusion that John is an instance of an intersection of
> >	     Person and Employee.
> >RAISED BY:   Peter F. Patel-Schneider
> >REFERENCE:   too numerous to find a definitive reference
> Peter, why do you characterize this as the *semantics* being too 
> weak? To me that suggests that you have in mind that there is a 
> 'real' or 'intended' notion of inference for DAML+OIL and that the 
> semantics fails to capture it properly. Is that a fair assumption, 
> and if so, can you give us any more details of what this other notion 
> of inference might be, or how we can determine what inferences should 
> be sanctioned by a correct MT that are not sanctioned by the current 
> MT?
> Pat

What I am trying to get at is that the semantics of DAML+OIL does not
produce all the entailments one would like.  So, yes, I do have an intended
notion of entailment in DAML+OIL.  The sort of thing that I would like to
follow in OWL is:

   if john is a person
   and john is an employee
   then john is in the (an?) intersection of person and employee

DAML+OIL does not support this.

(The formal meaning of the above of course depends on what ``intersection
of person and employee'' means.  In DAML+OIL ``intersection of person and
employee'' is an instance of rdfs:Class, i.e., an element of the domain of
discourse, so making the above sort of inference supported by DAML+OIL in a
standard model theory extension of the DAML+OIL model theory
requires comprehension principles.  Different attitudes towards the status
of ``intersection of person and employee'' result in different kinds of
model theories.)

The intended meaning of inference that I am alluding to is similar to the
one that comes out of description logics (although there are lots of other
ways of thinking of it).

Received on Monday, 20 May 2002 11:15:38 UTC

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