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Re: proposal for working on the ontology language

From: Leo Obrst <lobrst@mitre.org>
Date: Wed, 12 Dec 2001 17:18:26 -0500
Message-ID: <3C17D7B1.9A25CDEC@mitre.org>
To: Raphael Volz <volz@fzi.de>
CC: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, www-webont-wg@w3.org
Thanks for the reference to the MMF stuff, Raphael: I wasn't aware of
it. Are you actively involved in this? You know we have some interest in
our group in trying to correlate our emerging vision of the Web Ontology
Language (WOL?) with UML, and perhaps other languages.

Leo

> Raphael Volz wrote:
> 
> If one has a modifiable meta level then one must be able to declare
> the semantics of newly defined primitives. UML has an extensible
> meta level but is ambiguous due to it's poorly defined (natural
> language)
> semantics, which hinders interoperability.
> 
> MMF tries to clarify that (it is a UML 2.0 proposal backed by IBM and
> Rational) using a model-theoretic semantics, which states what models
> are valid instances of any particular meta-model expressed in MML.
> See http://www.cs.york.ac.uk/puml/mmf/index.html for details.
> 
> Regards,
> 
> Raphael
> 
> -----Original Message-----
> From:   Peter F. Patel-Schneider
> Sent:   Wed 12/12/2001 4:50 PM
> To:     lobrst@mitre.org
> Cc:     www-webont-wg@w3.org
> Subject:        Re: proposal for working on the ontology language
> 
> Precisely.  Systems like Protege have a meta-level in the same sense
> that
> RDF has.  The way you create classes is to create instances of a
> metaclass.
> However, this is not a modifiable meta level.
> 
> A modifiable meta level would have something like what
> rdfs:ConstraintProperty was supposed to do.  That is, it would be
> possible
> to either 1/ change the way that existing class constructs worked or
> 2/ add
> fundamentally different class constructs by creating metaclasses.
> One (very hard) example would be to add defaults to a formalism
> without
> them.  Another (simpler) example would be to add range constraints to
> a
> formalism without them.
> 
> There have been a number of proposals for this sort of meta level,
> going
> back to the 1970s.  However, I'm not aware of any (continuing) use of
> these
> facilities, except in object extensions to LISP-like programming
> languages (e.g., CLOS).  I should have ruled this out from the start.
> 
> peter
> 
> From: Leo Obrst <lobrst@mitre.org>
> Subject: Re: proposal for working on the ontology language
> Date: Tue, 11 Dec 2001 18:30:48 -0500
> 
> > Peter,
> >
> > Although not formalized, I am thinking of Protege (not that it's
> > modifiable, you can only add consistently defined new meta-classes).
> I
> > also think of CLOS, again as mostly an unformalized language.
> >
> > "Peter F. Patel-Schneider" wrote:
> > >
> > > From: Leo Obrst <lobrst@mitre.org>
> > > Subject: Re: proposal for working on the ontology language
> > > Date: Tue, 11 Dec 2001 18:14:42 -0500
> > >
> > > [...]
> > >
> > > > I also note that there is no meta level to DAML+OIL and I think
> that was
> > > > a conscious choice, no?, though I don't know the history of that
> > > > decision. Sometimes having a modifiable meta level is a very
> good thing
> > > > (future language extensions, e.g.)
> > > >
> > > > Leo
> > >
> > > I would be very interested in hearing of cases where a modifiable
> meta
> > > level was actually used.  I wouild be even more interested in
> hearing of
> > > such cases that also involved a logical formalism.
> > >
> > > peter
> >
> > --
> > _____________________________________________
> > Dr. Leo Obrst         The MITRE Corporation
> > mailto:lobrst@mitre.org Intelligent Information
> Management/Exploitation
> > Voice: 703-883-6770   7515 Colshire Drive, M/S W640
> > Fax: 703-883-1379       McLean, VA 22102-7508, USA

-- 
_____________________________________________
Dr. Leo Obrst		The MITRE Corporation
mailto:lobrst@mitre.org Intelligent Information Management/Exploitation
Voice: 703-883-6770	7515 Colshire Drive, M/S W640
Fax: 703-883-1379       McLean, VA 22102-7508, USA
Received on Wednesday, 12 December 2001 17:19:09 GMT

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