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Re: Qualified Cardinality Constraints

From: Volker Haarslev <haarslev@cs.concordia.ca>
Date: Tue, 9 Mar 2004 19:09:16 -0500
Message-Id: <2B1E47E0-7227-11D8-B131-000393CDF1A6@cs.concordia.ca>
Cc: "Dickinson, Ian J" <Ian.Dickinson@hp.com>, Jim Hendler <hendler@cs.umd.edu>, Guus Schreiber <schreiber@swi.psy.uva.nl>, public-webont-comments@w3.org, Ian Horrocks <horrocks@cs.man.ac.uk>, Peter Patel-Schneider <pfps@research.bell-labs.com>, Ralf Möller <r.f.moeller@tu-harburg.de>
To: Alan Rector <rector@cs.man.ac.uk>

On 9-Mar-04, at 17:27, Alan Rector wrote:

> Jim, Guus, all
> Firstly congratulations on getting the recommendation through.
> Secondly, now that it is through at this stage, I would like to see a 
> timely return to the issue of qualified cardinality restrictions.
> I have been putting together a list of patterns, best practices, etc. 
> and working on various alternative templates for different 
> applications.  Almost without exception, the ontologies which aim for 
> non-trivial re-use require qualified cardinality restrictions, most 
> commonly to be able to say that something can have one of each of a 
> series of values.
> Without qualified cardinality restrictions one has a choice: a) ignore 
> the cardinality constraint altogether; b) create an extra property 
> which mirrors the classes in the ontology, so that one ends up with 
> dozens of subproperties whose sole purpose is to limit cardinality. 
> Furthermore, b) still does not capture the notion correctly because 
> the parent property still does not carry the cardinality restriction. 
> Therefore one has to implement things in tools and do complex 
> translations.
> It also comes out repeatedly in teaching cases in responses to 
> questions from students.
> Furthermore, if it isn't in the standards soon, implementations won't 
> include them.  Already this is presenting problems.
> All my previous arguments apply, but I include a list of recently 
> encountered examples below.
> There has just been a "Best Practices" initiative launched.  It would 
> be unfortunate if there were not a pronouncement on this issue in time 
> for at least some comment in a best practice document.  Otherwise, 
> many "best practices" will have to be seriously compromised.
> I would like to point out that those  concerned about the removal of 
> qualified cardinality restrictions withdrew our objects reluctantly in 
> order to allow the standard to be approved quickly but on the 
> understanding that this issue would be addressed speedily once the 
> standard was adopted.  It now has been adopted.
> I would therefore like to ask formally how the  issue of qualified 
> cardinality restrictions is to be addressed and when.

Hi all,

I second the motion of Alan. I do not see any computational problems by 
introducing qualified number restrictions into OWL DL. For instance, 
Racer incorporates two innovative optimization techniques for 
efficiently dealing with qualified number restrictions. These were 
published at IJCAR and the DL workshop. Racer already accepts an OWL 
extension (in the spirit of DAM+OIL) that allows the specification of 
qualified number restrictions.

Regards, Volker Haarslev
Volker Haarslev, Dr. habil.
Associate Professor
Computer Science Department
Concordia University
1455 de Maisonneuve Blvd. W.
Montreal, Quebec  H3G 1M8, Canada
Phone: +1 (514) 848-2424 ext. 3049
Fax: +1 (514) 848-2830
Received on Tuesday, 9 March 2004 19:09:20 UTC

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