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Re: DAML-ONT: the case for closedness

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 19 Oct 2000 09:26:40 -0400
To: Frank.van.Harmelen@cs.vu.nl
Cc: www-rdf-logic@w3.org
Message-Id: <20001019092640F.pfps@research.bell-labs.com>
From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Subject: Re: DAML-ONT: the case for closedness
Date: Thu, 19 Oct 2000 14:57:20 +0200

> 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.
> 
> 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. 

Jerome may want something a bit different, namely a primitive class (i.e.,
a class that has only necessary conditions for membership) that cannot be
further refined.  I'm not sure what good this is, except perhaps in the
philosophy of religion (unknowable mysteries whose limits of knowledge have
been reached, etc., etc.).  If some other modeller wants to augment the
properties of a primitive class then I don't see why this should not be
allowed.  Of course this other modeller can get into trouble by adding
properties that should not be there, but I don't see that the goal of a
modelling language is to prevent modellers from doing wrong things, nor
do I see that there is any way of preventing such mistakes in any case,
even if that was desired.

peter
Received on Thursday, 19 October 2000 09:28:03 GMT

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