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Re: DAML: restricting number of elements in a list

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Sat, 9 Feb 2002 23:15:22 +0000
Message-ID: <15461.44426.903217.89531@cs.man.ac.uk>
To: Ken Baclawski <kenb@ccs.neu.edu>
Cc: Steven Gollery <sgollery@cadrc.calpoly.edu>, www-rdf-logic@w3.org
On February 7, Ken Baclawski writes:
> The daml:item property relates a list to each of its elements.  One can
> impose a daml:minCardinality restriction on the daml:item property to
> ensure that the number of vertices in a polygon is at least 3. 
> 
> Ken Baclawski
> Ken@Baclawski.com
> UBOT Project

I am afraid that this is a common misconception. You can write such a
thing, but if you read the language specification you will find that
daml+oil does not provide any semantics for it, so it does not have
the effect that you desire (in fact, from the point of view of
daml+oil, it has no effect whatsoever). 

Supporting this kind of statement would have resulted in a language
that was able to modify its own meaning. We did not want to even try
to define a semantics for such a language, much less write software
(e.g., reasoners) to support it.

Regards, Ian


> 
> On Wed, 6 Feb 2002, Steven Gollery wrote:
> 
> > I'm working on an ontology in DAML that includes some geometric
> > concepts. I would like to be able to somehow define a property Vertices
> > whose domain is the Polygon class and whose range is ordered collections
> > of instances of the Point class, where the length of the ordered
> > collection is at least three.
> > 
> > It would be fairly straightforward to say that each Polygon must have at
> > least three values of a Vertex property which is restricted to class
> > Point, but that would lose the idea the vertices have an order -- the
> > order is obviously a fundamental part of the semantics for the polygon.
> > 
> > Does DAML provide any way to restrict the number of elements in a list?
> > Or is there some other way to do what I need here?
> > 
> > Thanks in advance,
> > 
> > Steve Gollery
> > sgollery@cadrc.calpoly.edu
> > 
> > 
> 
Received on Saturday, 9 February 2002 18:17:04 GMT

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