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Re: Classes and predicates as first class objects

From: Bob MacGregor <macgregor@ISI.EDU>
Date: Thu, 15 Aug 2002 14:50:30 -0700
Message-ID: <01db01c244a5$c82ed440$f8800980@STRIKER>
To: "Deborah McGuinness" <dlm@KSL.Stanford.EDU>, "Ian Horrocks" <horrocks@cs.man.ac.uk>
Cc: "R.V.Guha" <guha@guha.com>, <www-rdf-logic@w3.org>

This discussion started not as a question about the merits of DLs, but
asked what you get when you sacrifice the ability to treat classes/predicates
as arguments to other predicates.  Slightly paraphrasing:

> > > Clearly, not allowing this feature (classes and arc labels as
> > > first class objects) buys description logics something.

Please correct me if I'm wrong, but my recollection is that CLASSIC allowed
second-order syntax, and in fact made some claims as to the utility of doing
so.  I my recollection is correct, then its not the case that we have to make this
particular sacrifice to achieve the "benefits" of a DL.  Rather, the trade-off
exists only for certain subclasses of DLs.

- Bob

----- Original Message ----- 
From: "Deborah McGuinness" <dlm@KSL.Stanford.EDU>
To: "Ian Horrocks" <horrocks@cs.man.ac.uk>
Cc: "R.V.Guha" <guha@guha.com>; <www-rdf-logic@w3.org>
Sent: Thursday, August 15, 2002 14:31
Subject: Re: Classes and predicates as first class objects


> 
> to support Ian's last statement that DLs are and have been used in a wide
> variety of applications and also because people had previously asked for some
> example applications,
> i include a paragraph from a message i sent a while ago on a related topic
> (full message available from
> http://lists.w3.org/Archives/Public/www-rdf-logic/2001Feb/0044.html)
> 
> This was just a list of some variety of applications of an earlier description
> logic - CLASSIC - but it shows applications with references in broad areas.
> 
> "I have helped people use CLASSIC in a series of large applications; the
> largest and longest lived was a family of configurators called PROSE/QUESTAR
> [1].  This included 17 configurators, some of which were used for a decade.
> They were used by AT&T and Lucent.  Other major application areas include data
> 
> archeology  [2], software discovery [3], query expansion [4], query answering
> [5], plan representation [6],  knowledge based software engineering [7], and
> other domains.   We also spent time considering the usability issues of the
> language [8,9]."
> 
> Most if not all of these applications (and the application areas in general)
> benefited greatly from having the qualities that Ian refers to of reliable and
> efficient reasoning.
> 
> Deborah
> 
> [1] Deborah L. McGuinness and Jon Wright. ``An Industrial Strength Description
> 
> Logic-based Configurator Platform''. IEEE Intelligent Systems, Vol. 13, No. 4,
> 
> July/August 1998, pp. 69-77. )
> 
> [2] Ronald J. Brachman, Peter G. Selfridge, Loren G. Terveen, Boris Altman,
> Alex Borgida, Fern Halper, Thomas Kirk, Alan Lazar, Deborah L. McGuinness,
> Lori Alperin Resnick. ``Integrated Support for Data Archaeology.'' In
> International Journal of Intelligent and Cooperative Information Systems, 2:2
> 1993, pages 159--185.
> 
> [3] P. Devanbu, R.J. Brachman, P.G. Selfridge, B.W. Ballard: "LaSSIE: A
> knowledge-based software information system" Communications of the ACM,
> 34(5):35--49, May 1991.
> 
> [4] Deborah L. McGuinness. ``Ontological Issues for Knowledge-Enhanced
> Search''. In the Proceedings of Formal Ontology in Information Systems, June
> 1998. Also in Frontiers in Artificial Intelligence and Applications,
> IOS-Press, Washington, DC, 1998.
> 
> [5] Alon Y. Levy, Anand Rajaraman and Joann J. Ordille, ``Query Answering
> Algorithms for Information Agents'' Proceedings of the 13th National
> Conference on Artificial Intelligence, AAAI-96, Portland, Oregon, August,
> 1996.
> 
> [6] P. Devanbu , D. Litman , CLASP - a plan representation and classification
> scheme for a software information System,  Published in Artificial
> Intelligence , 1996
> 
> [7] P. Devanbu , M. Jones , The use of description logics in KBSE systems.
> Published in ACM Transactions on Software Engineering and Methodology , 1997
> 
> [8] Deborah L. McGuinness and Peter F. Patel-Schneider. ``Usability Issues in
> Knowledge Representation Systems''. In Proceedings of the Fifteenth National
> Conference on Artificial Intelligence, Madison, Wisconsin, July, 1998. This is
> 
> an updated version of ``Usability Issues in Description Logic Systems''
> published in Proceedings of International Workshop on Description Logics, Gif
> sur Yvette, (Paris), France, September, 1997.
> 
> [9] Ronald J. Brachman, Alex Borgida, Deborah L. McGuinness, and Peter F.
> Patel-Schneider. "Reducing" CLASSIC to Practice: Knowledge Representation
> Theory Meets Reality. In Artificial Intelligence 114(1-2) pages 203-237,
> October
> 
> Ian Horrocks wrote:
> 
> > On August 14, R.V.Guha writes:
> > >
> > >
> > >  Much of the debate around layering of OWL on top of RDF and RDFs boils
> > > down to whether the Semantic Web should treat classes and arc labels as
> > > first class objects, about which arbitrary new kinds of statements can
> > > be made.
> > >
> > > This is an important architectural choice which has to take into account
> > > results from systems that have been built. Looking at what was learnt
> > > from such systems would probably be productive ...
> > >
> > >  RDF, which has been largely influenced by the experimental "scruffy"
> > > side of AI has gone the route of many experimental AI systems (starting
> > > from KRL, RLL, .... CycL) and incorporated these as first class objects.
> > > In my experience, and the experience of the builders of these systems,
> > > this has been a useful feature. Description Logics, which come from the
> > > more "neat" side of AI chose not to allow this ...
> > >
> > > Clearly, not allowing this feature buys description logics something.
> > > Ian, maybe you could explain exactly what this is and how it has been
> > > found useful in large DL systems that have been built?
> >
> > Work on DLs has resulted in the development of a family of logical
> > languages with precisely defined semantics and well understood
> > computational properties. They are (almost invariably) decidable
> > subsets of FOL and are closely related to propositional modal and
> > dynamic logics.  For many of these languages, provably sound and
> > complete decision procedures have been devised. Several DL systems
> > have been based on optimised implementations of these algorithms, thus
> > providing users with reasoning services that are both reliable and
> > efficient. These systems are being used in a wide range of
> > applications, e.g., in medical-informatics, bio-informatics, chemical
> > engineering and geographical information systems.
> >
> > Ian
> >
> > >
> > > thanks,
> > >
> > > guha
> > >
> > >
> > >
> > >
> 
> --
>  Deborah L. McGuinness
>  Knowledge Systems Laboratory
>  Gates Computer Science Building, 2A Room 241
>  Stanford University, Stanford, CA 94305-9020
>  email: dlm@ksl.stanford.edu
>  URL: http://ksl.stanford.edu/people/dlm/index.html
>  (voice) 650 723 9770    (stanford fax) 650 725 5850   (computer fax)  801 705
> 0941
> 
> 
Received on Thursday, 15 August 2002 17:48:54 UTC

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