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Re: Possible confusion in Reference

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 28 Apr 2003 08:43:31 -0400 (EDT)
Message-Id: <20030428.084331.68547837.pfps@research.bell-labs.com>
To: heflin@cse.lehigh.edu
Cc: www-webont-wg@w3.org

To: heflin@cse.lehigh.edu
Cc: www-webont-wg@w3.org
Subject: Re: Possible confusion in Reference
From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
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From: Jeff Heflin <heflin@cse.lehigh.edu>
Subject: Possible confusion in Reference
Date: Fri, 25 Apr 2003 17:05:15 -0400

> 
> I was looking through the reference today and I think the description of
> owl:sameAs in section 5.2 is misleading. It says:
> 
> In OWL Full, where class can be treated as instances of (meta)classes,
> we can use the owl:sameAs construct to define class equality, thus
> indicating that two concepts have the same intensional meaning.
> 
> (btw, note "where class can" should be "where classes can")
> 
> I believe that in fact sameAs has an even stronger interpretation: that
> the classes are the same resource! (Peter, please correct me if I'm
> wrong here). 

This is correct.  owl:sameAs (and owl:sameIndividualAs) provides
co-denotation. 

> Note the implications of this. If one class has some
> meta-property, such as author, label, last change date or whatever, then
> any class that is "sameAs" it also has the same values for those
> properties. 

Correct.

> Chances are, this is not what is usually intended. 

Hmm.  Sometimes it is, at least for those who think in RDF.

> However,
> the reference implies this is the preferred way to map two class
> concepts that have the same intensional meaning. Unfortuantely, OWL
> doesn't really have a mechanism for truly stating that two classes have
> the same intensional meaning. 

How about owl:equivalentClass?

> That would require us to somehow separate
> meta-properties that are about a particular resource from those about
> the concept it denotes. 

I'm not sure that OWL makes the distinction you describe here.  However,
there is a difference between the resource denoted by a URL and the class
extension of this resource.  owl:equivalentClass equates the latter without
affecting the former.  owl:sameAs and owl:sameIndividualAs equate the
former (and thus also equate the latter).

> Anyway, I think this issue should be explained
> and <footballTeam owl:equivalentClass us:soccerTeam /> should be the put
> forth as the preferred way for mapping these two classes.

It depends on what you want.  (I tend to view owl:equivalentClass as the
preferred mechanism, but I realize that others may differ.)

> Jeff

peter
Received on Monday, 28 April 2003 08:43:42 GMT

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