W3C home > Mailing lists > Public > public-owl-wg@w3.org > November 2007

Re: XML Schema datatypes

From: Carsten Lutz <clu@tcs.inf.tu-dresden.de>
Date: Thu, 15 Nov 2007 08:36:27 +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.4.64.0711150823060.29680@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. If you disgree, it would be
good to see a concrete example. But if such inferences are undesired,
why introduce bounded datatypes in the first place?

> And conceptual modeling isn't the only thing people do with OWL. People do 
> information integration which can require details about the types (consider 
> either ETL or distributed query). Or when reducing other formalisms, like 
> policy languages such as WS-Policy or XACML, to OWL, it can matter that you 
> have the actual datatypes involved.
>
> Finally, people *do* user RDF and OWL directly to work with semi-structured 
> data.
>
> So, I see your argument as supporting adding some additional, more general 
> types, to better support CM, not as an argument for eliminating various 
> representationally specific numeric types.
>
> As with numeric methods genearlly, the user must exercise care.

I can live with this view. This is the least we should do, i.e., giving
the users *the option* to work with unbounded datatypes.

>> We are defining an ontology language with a declarative semantics.
>
> I don't see that declarativity is an issue here.

With a procedural approach, you usually say (in a unique way) how a value
is computed. Also there we may hit upon a "gap" in a bounded datatype,
but then it is common to use rounding and this works just fine. With a 
declarative approach, there may easily be multiple ways to compute a value
(Jeremy's Celsius-Fahrenheit cycle is only a very simple example). 
Trying to do rounding there breaks things (even in the unary case!).

>> and (ii) the bounded datatypes of XML schema.
>
> Boundedness is an issue, but you can get that with integers and min and max. 
> Which we have.

If a user explicitly uses min and max in his modelling, he obviously
believes that the boundedness is crucial for the modelling. Then, he
should expect to have consequences that derive from that boundedness.
I cannot see that this is in any contradiction to what I have advocated.

> 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.

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 07:36:52 GMT

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