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Re: ISSUE: owl:Class name misleading; try owl:Set?

From: Dan Connolly <connolly@w3.org>
Date: 03 Jan 2003 00:38:37 -0600
To: "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>
Cc: www-webont-wg@w3.org
Message-Id: <1041575916.19697.191.camel@dirk.dm93.org>

On Wed, 2003-01-01 at 21:36, Peter F. Patel-Schneider wrote:
> > > I'm not sure what you are proposing here.  It seems to me that you are
> > > either saying that OWL classes already act like sets, which is incorrect,
> > 
> > I don't understand how it's incorrect. Please explain.
> See above.

OK, I'm convinced; after reading the semantics drafts
more closely, they don't say what I thought they said.
They don't guarantee that co-extensional owl classes are identical in
full owl.

Meanwhile, I don't see any reason it couldn't be
straightforwardly added.

> > > and thus that various names should be changed, or that OWL classes should
> > > act like sets, which I would oppose.
> > 
> > Why?
> Because it would be a last-minute change to OWL.  I don't think that the
> working group should be making changes to OWL from now on, except as
> required to fix problems.

I consider the sort of confusion expressed by McBride in
the message I cited to start this thread
indicative of a problem; we haven't explained
the difference between owl:Class and rdfs:Class
to the satisfaction of the community. (McBride's
are not the only comments to this effect that I've

When thinking about how to fix it, it occured to me that
renaming owl:Class to owl:Set and adding the
extensionality axiom (in full owl) would result
in a design that I think we could explain to
the satisfaction of the community.

If you don't find this appealing, I'll understand
if you don't feel any obligation to do anything
about it until I propose more details w.r.t.
changes to the semantics document.

Maybe a less invasive change, such as renaming
sameClassAs to sameMembersAs, is adequate and
less risky at this point.

I guess I can make my own dan:Set, and write
an extensionality axiom/rule for it. Sigh...
seems like such a handy thing to have in OWL.
I wish I had raised the issue sooner; I sent
it to rdf-comments ages ago, back in Nov 2001.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 3 January 2003 01:38:21 UTC

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