Re: Nulls, integrity, the closed world assumption and events

On Jan 8, 4:44 am, "David" <davi..._at_iinet.net.au> wrote:
> My point is that the following six conditions can't all be satisfied at
> once
> C1. use person(P,M,F) relation
> C2. don't allow nulls in M,F
> C3. enforce referential integrity on M,F
> C4. only allow finite number of persons in the domain
> C5. there are no cycles in the family tree
> C6. there is at least one person
>
> Obviously we must have C4, C5 and allow C6. I suggest that C2,C3 are
> important and therefore C1 should be dropped. ie the person(P,M,F)
> relation itself is "bad". Do you agree?

This analysis looks right to me.

Marshall Received on Tue Jan 09 2007 - 01:25:52 CET