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Re: defaults

From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Date: Tue, 22 Jan 2002 21:15:22 +0100
Message-ID: <3C4DC85A.437E8A61@cs.vu.nl>
To: www-webont-wg@w3.org
"Peter F. Patel-Schneider" wrote:

> I think of Michael's and Tim's suggestions as diametrically opposed.
> Michael is asking for something outside of the logic underlying OWL;  Tim
> is asking for some ability to affect the logic underlying OWL in an
> undefined way.

OK, I hadn't realised Tim was asking for this, the subsequent exchanges between you and him clarified this. So that places me in Michael's camp: "asking for something outside of the logic underlying OWL". 
 
> I view Frank's attempt to merge the two as the worst possible approach.
> (No joke.)  It manages, in one small package, to
> 1/ destroy any possible semantics we choose to supply
> 2/ make it look as if we are actually doing something about defaults
> 3/ give implementors permission to do whatever they want and claim that
>    they are just following the standard
> 
> > To be clear: I don't particularly like this approach (I don't think
> > anybody does), but it is  simply a practical way out of a thorny issue.
> 
> Expediency is terrible reason to do something that violates one's
> fundamental principles!

Oh dear, it's always a pleasant surprise to step on a landmine. 

To address your points in non-holy-war language:

1/ Michael's proposal will not destroy any semantics we choose to supply since, in your own words, it is "outside of the logic underlying OWL". Default expressions would be something without a formal semantics, but with an informally stated intent/purpose.

2/ It will be easy enough to make clear that we are not doing anything precise about defaults in whatever pieces we produce (be they formal or not)

3/ it will at least encourage implementors (and ontology constructors) to not encode anything silly about defaults in the formal part of the language (the point made by Michael's example, I believe). 

I find it very hard to believe that input-completion will do as much of the work as you claim it will. (See e.g. Enrico's message). Since there is so little consensus on how to do which kinds of defaults, why should be choose one particular one to be part of the language? Why not stop at providing a syntactic convention that people can use to (indeed) "do whatever they want"? And input completion could well be one of those things.

Frank.
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Received on Tuesday, 22 January 2002 15:16:25 GMT

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