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

Bob Badour wrote:
> JOG wrote:
> > Bob Badour wrote:
> >
> >>Marshall wrote:
> >>
> >>>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.
> >>
> >>Huh? Your solution basically achieves all of the above with the
> >>inconsequential difference that you used a different name for the
> >>relation in C1.
> >>
> >>Nowhere above does it mention the very consequential difference in
> >>referential integrity constraints, which is in fact the straw in the man.
> >
> > Hi Bob, if you were referring to my post then your last statement isn't
> > true. I emphasized the change in referential integrity constraints as
> > being important:
>
> You emphasized it and then David ignored it in his reply. If you look
> carefully, I think you will agree what you wrote appears "nowhere above"
> where I wrote "nowhere above".
>
>
> > JOG wrote
> >
> >>where P is the candidate key of _parentage_, but where P, M and F have
> >>enforced referential integrity (with a check constraint on sex) back to
> >>the _person_ relation
> >
> > Either I've missed your point or you had a heavy new years celebration
> > this year!
>
> You missed the point that David constructed a straw man by ignoring your
> point entirely.

Gotcha. All is clear. Happy new year. Received on Tue Jan 09 2007 - 15:01:12 CET