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Re: LANG: closing issue 4.6 (was Re: ADMIN: Draf agenda for July 25 telecon)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 24 Jul 2002 12:54:57 -0400
To: www-webont-wg@w3.org
Message-Id: <20020724125457W.pfps@research.bell-labs.com>

The question is about the relationship between equivalentTo and the
sameXxxAs properties, and what these four mean.

Option 1: The sameXxxAs properties are subproperties of equivalentTo.
          
In this option the standard way of saying that two classes have the same
extension is to make them denote the same object.  Because they denote the
same object, they must have the same extension.  Note that it is still
possible to have two classes have the same extension but not denote the
same object by using two subClassOf relationships, which then do not entail
that the two classes are sameClassAs.

This option depends on a strong view of classes as instances (and
properties as instances as well), because sameClassAs (and samePropertyAs)
only work through identifying the denotation of classes (or properties).

In this option the sameClassAs and samePropertyAs properties are not
particularly useful.  In this option equivalentTo has exactly the same
meaning as sameIndividualAs.  (Well, I suppose that it would be possible to
have some extra meaning for sameInvdividualAs, but I don't see any point
for this extra meaning.)

Option 2: The sameXxxAs properties are not subproperties of equivalentTo.

In this option the standard way of saying that two classes have the same
extension does not imply that they denote the same object.  Here
sameClassAs is exactly the same as having two subClassOf relationships.

This option does not depend on any particular answer to the classes as
instances issue.    



I vote for option 2.


Peter F. Patel-Schneider







From: Jeff Heflin <heflin@cse.lehigh.edu>
Subject: Re: LANG: closing issue 4.6 (was Re: ADMIN: Draf agenda for July 25    telecon)
Date: Wed, 24 Jul 2002 12:05:33 -0400

> 
> I also use equivalentTo all the time, and never use samePropertyAs,
> sameClassAs, or sameIndividualAs. If redundancy is the problem, let's
> get rid of the three sameBlankAs properties instead of the one. The
> three properties do two things:
> 
> 1) say that two concepts are the same
> 2) say that the two concepts are both properties, classes, or
> individuals
> 
> The first bit is what equivalentTo already does. The second bit is
> virtually useless, because any reasonable ontology will have stated
> whether a URI is a class or property elsewhere. Furthermore, these
> properties can still cause the class/instance confusion because I could
> say that foo is a class and then say foo sameInstanceAs bar.
> 
> If the problem is that people somehow see equivlalentTo as having
> meaning that is fundamentally different from the sameBlankAs properties,
> then I could live with renaming it to "sameAs."
> 
> Jeff
> 
> p.s. a bit of DAML+OIL history: At first, only equivalentTo was in the
> language. Some people argued for the need for a sameClassAs and
> samePropertyAs, and eventually even added sameIndividualAs. I didn't
> believe we needed them then, but didn't argue strongly because I could
> simply ignore them as long as equivalentTo was in the language and they
> were suproperties of it
> 
> Dan Connolly wrote:
> > 
> > On Wed, 2002-07-24 at 09:24, Jim Hendler wrote:
> > [...]
> > > Proposed:
> > >   I propose that we CLOSE issue 4.6 with the following resolution:
> > >
> > > We will remove the single construct "equivalentTo" from the language,
> > > as it is possible to use other features (sameClassAs, samePropertyAs,
> > > sameIndividualAs) to achieve its primary effect.
> > 
> > Ugh; I use equivalentTo all the time, and I hardly ever
> > use samePropertyAs, sameClassAs, or sameIndividualAs.
> > 
> > Hmm... I could perhaps live without equivalentTo.
> > I'll have to think about it.
> > 
> > --
> > Dan Connolly, W3C http://www.w3.org/People/Connolly/
> > see you in Montreal in August at Extreme Markup 2002?
Received on Wednesday, 24 July 2002 12:55:05 GMT

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