Re: Nulls, integrity, the closed world assumption and events
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 09 Jan 2007 14:05:39 GMT
Message-ID: <TiNoh.42639$cz.624804_at_ursa-nb00s0.nbnet.nb.ca>
>>JOG wrote:
>>
>>>Bob Badour wrote:
>>>
>>>>Marshall wrote:
>>>>
>>>>>On Jan 8, 4:44 am, "David" <davi..._at_iinet.net.au> wrote:
>>>>>
>>>>>>My point is that the following six conditions can't all be satisfied at
>>>>>>once
>>>>>> C1. use person(P,M,F) relation
>>>>>> C2. don't allow nulls in M,F
>>>>>> C3. enforce referential integrity on M,F
>>>>>> C4. only allow finite number of persons in the domain
>>>>>> C5. there are no cycles in the family tree
>>>>>> C6. there is at least one person
>>>>>>
>>>>>>Obviously we must have C4, C5 and allow C6. I suggest that C2,C3 are
>>>>>>important and therefore C1 should be dropped. ie the person(P,M,F)
>>>>>>relation itself is "bad". Do you agree?
>>>>>
>>>>>This analysis looks right to me.
>>>>
>>>>Huh? Your solution basically achieves all of the above with the
>>>>inconsequential difference that you used a different name for the
>>>>relation in C1.
>>>>
>>>>Nowhere above does it mention the very consequential difference in
>>>>referential integrity constraints, which is in fact the straw in the man.
>>>
>>>Hi Bob, if you were referring to my post then your last statement isn't
>>>true. I emphasized the change in referential integrity constraints as
>>>being important:
>>
>>You emphasized it and then David ignored it in his reply. If you look
>>carefully, I think you will agree what you wrote appears "nowhere above"
>>where I wrote "nowhere above".
>>
>>>JOG wrote
>>>
>>>
>>>>where P is the candidate key of _parentage_, but where P, M and F have
>>>>enforced referential integrity (with a check constraint on sex) back to
>>>>the _person_ relation
>>>
>>>Either I've missed your point or you had a heavy new years celebration
>>>this year!
>>
>>You missed the point that David constructed a straw man by ignoring your
>>point entirely.
>
> Gotcha. All is clear. Happy new year.
Date: Tue, 09 Jan 2007 14:05:39 GMT
Message-ID: <TiNoh.42639$cz.624804_at_ursa-nb00s0.nbnet.nb.ca>
JOG wrote:
> 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.
Happy New Year! Received on Tue Jan 09 2007 - 15:05:39 CET