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Re: Case for Reinstatement of Qualified Cardinality Restrictions

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 17 Apr 2003 12:21:04 -0500
Message-Id: <p05111b0ebac481c17b3c@[]>
To: Jim Hendler <hendler@cs.umd.edu>
Cc: "Jonathan Borden" <jonathan@openhealth.org>, "webont" <www-webont-wg@w3.org>

>At 6:20 PM -0400 4/16/03, Jonathan Borden wrote:
>>As I recall the discussion at the Amsterdam F2F -- I had wondered if such
>>features would be needed by biomedical ontologies and thought that I was
>>told that this wasn't the case.
>>The use cases he cites are compelling (at least to me), and if indeed
>>qualified cardinalities *are* needed to support these then I strongly
>>support reopening the issue.

I agree. Seems to me that its up to those who think not, to respond 
to Alan's examples with counter-arguments, eg showing that the 
workarounds that he dislikes aren't so bad after all, or that there 
are better ones.

>I am worried that the feature most complained about in Daml+oil and 
>also the ones most misused were these.

On the other hand, maybe that was partly due to the truly awful 
terminology used, and the fact that the DAML tutorials placed very 
little emphasis on them. And that this whole ontology thing was new 
to many DAML users, whereas Alan is speaking from a much more 
sophisticated community.

>Let me make a suggestion -- if we were to decide to include these, 
>we would need to write the one-paragraph, easy to understand 
>explanation that would go in the Overview -- anyone want to take a 
>stab at a suggested one?

Well, the guide only talks about OWLLite, which has limited 
cardinality in any case so wouldnt work for Alan's examples, but here 
goes as a sketch:

3.4a OWL  Restrictions


minCardinalityFrom: This refer to a class and a number. It 
generalizes someValuesFrom by requiring at least that number of 
values for the property to be of the type described by the class. 
Note that this says nothing about values of the property in other 
classes. [someValuesFrom P] is equivalent to [minCardinalityFrom P 1]

maxCardinalityFrom: this restriction requires that the number of 
values for the property which are of the type described by the class 
be no more than the number given. Note that this says nothing about 
values of the property in other classes.  [allValuesFrom P] is 
equivalent to [maxCardinalityFrom [Complement P] 0]

CardinalityFrom:  This restriction is provided as a convenience when 
it is useful to state that there is an exact number of values of a 
property in a particular class, eg [Hand partOf CardinalityFrom 
Fingers 5] says that the number of partsOf a Hand that are classified 
as Fingers must be 5.  Note that this says nothing about values of 
the property in other classes; for example, a hand may also have 
parts which are the palm and the back, in addition to the 5 fingers.

minCardinality:  this restriction simplifies minCardinalityFrom by 
ignoring the class; it simply sets a lower bound on the total number 
of values of the property, in effect treating the restricting class 
to be the universe.  In OWL-DL, [minCardinality n] is equivalent to 
[minCardinalityFrom owl:Thing n] for individual properties and to 
[minCardinalityFrom rdfs:Literal n] for datatype properties; in 
OWL-Full, it is equivalent to [minCardinalityFrom rdfs:Resource n].

similarly for maxCardinality, Cardinality.

>  -JH
>p.s. Any change that would require us to change every document and 
>that is exposed by test cases makes me nervous at this late date -- 
>I'd want to see pretty strong support for the change...

Seems to me that Alan makes a devastating case in favor, and that 
although it is so late and all, that we will look kind of silly if we 
don't take it seriously. I wish I had thought of the atria/ventricles 
example. Particularly as he practically tells us what to do.

So, I vote to reinstate.


>>>  The following long message (from [1]) comes from Alan Rector to our
>>>  comments list, addressing the issue of the qualified constraints -
>>>  basically, he's asking us to reopen issue 3.2 Qualified Cardinality
>>>  constraints.  Guus and I would like to hear the WG's feelings on
>>>  this.  Since there's no specific document addressed (although it
>>>  would require changes in every document), Guus and I will handle this
>>>  email and its response.
>>>    -JH
>>>  [1]
>Professor James Hendler				  hendler@cs.umd.edu
>Director, Semantic Web and Agent Technologies	  301-405-2696
>Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
>Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)

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Received on Thursday, 17 April 2003 13:21:12 UTC

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