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Re: Proposed simplification of datatype expressions

From: Sean Bechhofer <seanb@cs.man.ac.uk>
Date: Thu, 13 Mar 2003 16:52:41 +0000 (GMT Standard Time)
To: Dan Connolly <connolly@w3.org>
cc: Ian Horrocks <horrocks@cs.man.ac.uk>, <www-webont-wg@w3.org>
Message-ID: <Pine.WNT.4.44.0303131645480.288-100000@potato>

On Thu, 13 Mar 2003, Dan Connolly wrote:

>
> On Thu, 2003-03-13 at 10:47, Ian Horrocks wrote:
> > I know this is rather last-minute, but I would like to propose a
> > couple of small simplifications to the language that would
> > significantly improve ease of implementation of datatype reasoning in
> > both DL and Lite.
> >
> > 1. Change the specification of cardinality constraints so that they
> > can only be applied to individual valued properties and not to data
> > valued properties. This seems to be a relatively small loss as most
> > data valued properties turn out to be functional, and it is hard to
> > think of realistic examples where local/arbitrary-valued cardinality
> > constraints are required.
>
> I can support going to 0/1/many. But constraining a property
> to be functional is a cardinality constraint, no?
> I don't think I'm quite clear on what you're after.

I think that what Ian is suggesting that you're still allowed to assert
whether a data valued property is functional or not, but that arbitrary
cardinality constraints involving data valued properties can't be used in
descriptions. So, for example, we can still say that age is functional,
and thus everyone can only have at most one age, but we can't form a
description of:

"people who have at least three values for property x."

where x is a data valued property. I, too, struggle to think of an example
where one would actually want to use such a construct (but am open to
suggestion)....

	Sean

-- 
Sean Bechhofer
seanb@cs.man.ac.uk
http://www.cs.man.ac.uk/~seanb
Received on Thursday, 13 March 2003 11:53:12 GMT

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