RE: Proposed simplification of datatype expressions

From: "Peter Crowther" <>

> > From: pat hayes []
> > >"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).

>I have to say
> that I'm not convinced that any of the following are naturally
> datatypes:
> - homes
> - sources of income

If people want to model incomes in numbers, then it is *very* natural for them to
use datatypes.

Jeff Z. Pan  ( )
Computer Science Dept., The University of Manchester

> - children
> - nationalities
> - travel to a given nation during a date range
> Nationality, in my view, comes closest; but why is this better as a
> datatype than an object?
>   - Peter

Received on Friday, 21 March 2003 12:35:21 UTC