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

On Jan 8, 5:06 pm, Bob Badour <bbad..._at_pei.sympatico.ca> 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.

I'm a little unclear who the "you" in the "your solution basically" sentence
above is, since I didn't propose a solution. I just agreed with the claim that we can't simultaneously satisfy C1 - C6.  

Marshall Received on Tue Jan 09 2007 - 02:37:49 CET