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Re: XML Schema datatypes

From: Carsten Lutz <clu@tcs.inf.tu-dresden.de>
Date: Thu, 15 Nov 2007 11:28:48 +0100 (CET)
To: Bijan Parsia <bparsia@cs.man.ac.uk>
Cc: "Web Ontology Language (OWL) Working Group WG" <public-owl-wg@w3.org>
Message-id: <Pine.LNX.4.64.0711151114040.24037@frege.inf.tu-dresden.de>

On Thu, 15 Nov 2007, Bijan Parsia wrote:
>
>>>> *We* are *not* defining a schema language for (stored) data in the
>>>> sense of XML Schema. So it is a valid question whether or not the XML
>>>> Schema datatypes are also good for our (different) purposes. I believe
>>>> they are not.
>>> 
>>> I think this is too strong. Sometimes users use OWL for *high level* 
>>> conceptual modeling, but sometimes one is refining the conceptual model a 
>>> bit based on some more concrete aspects. why should they have to switch 
>>> out from OWL just because they need to account for representation limits? 
>>> What about modeling database schemas?
>> 
>> I feel that deductions that actually *rely* on the boundedness or fixed
>> precision are (almost?) never desired.
>
> Even if so, they may rely on disjointness of types. For example, if I'm 
> modeling an attribute with a float value in one schema and an integer value 
> in another, it's useful to get a class if I claim classes with these 
> (functional) attributes are equivalent.

You could also say: If you *claim* these are equivalent, you should
not get an inconsistency, but rather deduce that the class which has
floats can only have integer values, stored as floats. That's what you
would get when using mathematical datatypes instead of machine
datatypes. In your view, you are reasoning about the representation of
the class. In my view, I reason about the class.

I claim that the representation-independent view is much more
important for an ontology language. Still, you are right that there
are conceivable applications that want machine datatypes. I admit that
my view that these should be represented in terms of mathematical
datatypes is maybe a bit too theoretically motivated.

>>> I don't see that as a fix. And if the issue is merely boundedness then 
>>> we'd have to chuck user defined datatypes on the integers.
>> 
>> I disagree.
>
> If the issue which is sufficient to remove a dataype is that it is *bounded*, 
> then obviously all bounded types should go. Your more sophisticated version 
> is that the particular boundedness stemming from some of the built-in types 
> is undesirable from a modeling perspective *and* has counterintuitive 
> results.

Yes, and XML Schema datatypes *force* the user to work with a bound
that is motivated by data representation. This is different from
*allowing* them to work with bounds.

Maybe we are not that far apart and could simply sum up the current 
discussion as: we both want to have mathematical datatypes in OWL 1.1,
and we believe (maybe to a different extent) that standard users have
to be educated regarding the consequences of choosing an XML Schema 
datatype vs a mathematical one.

This education issue is not to be taken lightly. If we offer both XML
schema datatypes and mathematical datatypes, there is a fair chance
that users will use the XML ones simply because XML is cool and sounds
more familiar, and then be surprised about the results.

greetings,
 		Carsten

--
*      Carsten Lutz, Institut f"ur Theoretische Informatik, TU Dresden       *
*     Office phone:++49 351 46339171   mailto:lutz@tcs.inf.tu-dresden.de     *
Received on Thursday, 15 November 2007 10:29:07 GMT

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