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RE: Proposed simplification of datatype expressions

From: Evan Wallace <ewallace@cme.nist.gov>
Date: Fri, 21 Mar 2003 13:46:40 -0500 (EST)
Message-Id: <200303211846.NAA09746@clue.msid.cme.nist.gov>
To: www-webont-wg@w3.org, phayes@ai.uwf.edu


Jeff Pan wrote:

>From: "Peter Crowther" <Peter.Crowther@networkinference.com>
>
>> > From: pat hayes [mailto:phayes@ai.uwf.edu]
>> > >"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)....
>> >
>> > People who own three or more homes, people with at least three
>> > sources of income, people with at least three children, people with
>> > with at least three nationalities, people who have travelled to more
>> > than three foreign nations during the last six months,....
>>
>> All good examples of cardinality contraints to objects;
>
>Well, that usually depends on what you want to model. Good examples of
>cardinality constraints to objects can also be good examples of cardinality
>constraints to data values in some situations (see below).

This question of "what you want to model" is an interesting point.  It
seems to me that there are times that one wants to collapse some walk
though "conceptual" objects and properties into a simple datavalue 
(oo:attribute), particularly in cases where the other properties of 
intermediate objects are not of interest to a particular set of 
applications.  I don't mean derived values, but rather models/ontologies
simplified for expected use.  

Then there is also the notion of "external key" which may still be 
important for working with data associated with 2 otherwise inconsistent 
ontologies which may provide different views over overlapping sets of real 
world objects.  

Perhaps, these views are antithetical to the way of thinking in the 
Semantic Web world?  If so, I don't care enough about this to engage in 
theological discussions.  I do, however; believe that it is important to
maintain the ability to express oneof datavalue sets.  There are plenty of
design-to-order style parametric product models which allow only a small
set (unordered) of values for the parameter.  I can also think of querying
scenarios where cardinality restrictions would apply to DataProperties:
  Find all the new MINIs with two colors.  
  Find all US car models in 1958 produced with 3 colors (tri-color option). 

If we revisit the decision made yesterday, I would object to adopting
Ian's proposed simplification of datatype expressions.

-Evan



-Evan
Received on Friday, 21 March 2003 13:46:56 GMT

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