RE: Amsterdam f2f issue 1

>-----Original Message-----
>From: Pat Hayes []
>Sent: Thursday, 18 April, 2002 2:28
>To: tim finin
>Subject: Re: Amsterdam f2f issue 1
>I suggest HasOnlyOne for UniqueProperty and IsTheOnlyOne for 
>UnambiguousProperty. Then one could say things like HasOnlyOne Father 
>(or IsTheOnlyOne FatherOf.)

In my day to day work I have come across a further distinction between
two 'types' of IsTheOnlyOne that I believe one may need to make when
dealing with properties with cardinalities greater than one. It is
perhaps best to explain with examples.

Start with a class Woman and a property Children, where there is a
priori no upper bound on the cardinality of the instances of persons
that we may associate with each instance of Woman via the Children
property. It then becomes most natural to regard a *collection* of
person instances as the object associated with each instance of Woman by
way of the Children property. Now, if in my modelling I wish to accept
as a biological or social convention that no two women can be the
mothers of one and the same child, then I may wish to express this by
applying to the Children property the constraint 'IsTheOnlyOne', with
the intended semantics being that given, say, an instance Emma and an
instance Victoria, if Emma != Victoria then the collection
Children(Emma) is *disjoint* from the collection Children(Victoria).

In another context, I may have a class Committee with a property
Members, again with cardinality greater than one, and in the domain I am
modelling it may be that one wishes to enforce a rule that states that
although two separate committees may have an overlap of members, no two
commitees may have exactly the same list of members. Again I may be
tempted to express this by applying to the Members property the
constraint 'IsTheOnlyOne', where now the intended semantics is that
given, say, an instance 'ForeignAffairs Committee' and an instance
'HomeAffairs Committee', if ForeignAffairs Committee != HomeAffairs
Committee then Members(ForeignAffairs Committee) != Members(HomeAffairs
Committee) in the sense of *set inequality*, rather then disjointness.

Obviously these two different semantics cannot both be the meaning
ascribed to IsTheOnlyOne, but expressing these  is something that we may
wish to enable, thus requiring two different syntactical expressions.

-- Ziv

Received on Thursday, 18 April 2002 14:32:35 UTC