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

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 09 Jan 2007 01:06:24 GMT
Message-ID: <kUBoh.42491$cz.622226@ursa-nb00s0.nbnet.nb.ca>

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. Received on Mon Jan 08 2007 - 19:06:24 CST