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Re: DAML-ONT: the case for closedness

From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Date: Thu, 19 Oct 2000 14:57:20 +0200
Message-ID: <39EEEFB0.A522B805@cs.vu.nl>
CC: www-rdf-logic@w3.org
To: unlisted-recipients:; (no To-header on input)
Je'ro^me Euzenat wrote:

> [FvH: He wants to express the distinction between:]
> - "a car is a vehicle with four wheels" and nothing else can be said
> about cars (but if course you can have refinement of the car concept,
> but these are not all the cars)
> and
> - "a car is a vehicle with four wheels" and you can add many more
> assertions about cars in general which will restrict the meaning of
> that concept that I do not know to characterize more precisely and
> that you can refine depending on your needs.
>         Currently DAML-ONT only permits to express the second. I
> suggested that in order to be trusted, ontologies must have some
> stable bases on which you know you can build. This might help
> adopters to feel safer with these ontologies and might contribute a
> bit to the web of trust.

This is exaclty what is known as "defined classes": classes for which necessary and sufficient conditions are given, and for which it is stated that these conditions are indeed necessary and sufficient for this class. 

They are part of many description logics. They are also a modelling primitive in OIL. Their absence from DAML has been discussed before in another thread. 

Quote from an earlier message from Deborah McGuinness:

> examples are available in the OIL whitepaper at:
> http://www.ontoknowledge.org/oil/downl/dialects.pdf
> type for oil is defined on page 6 of the document
> and examples using it are available in a few places including page 12 on the 
> definition of herbivore.

I think Jerome has given an eloquent motivation for why defined classes should be part of any Web-based ontology language. 

Frank van Harmelen.
Frank.van.Harmelen@cs.vu.nl              http://www.cs.vu.nl/~frankh
Department of AI, Faculty of Sciences,  Vrije Universiteit Amsterdam
de Boelelaan 1081a, 1081HV Amsterdam, The Netherlands
tel (+31)-20-444 7731 fax&voicemail (+31)-20-8722806
Received on Thursday, 19 October 2000 09:03:02 UTC

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