Re: Guessing?
Date: Tue, 8 Jul 2008 13:22:26 -0400
Message-ID: <InNck.11653$cW3.9262_at_nlpi064.nbdc.sbc.com>
"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
news:48738203$0$4049$9a566e8b_at_news.aliant.net...
> paul c wrote:
>
>> Brian Selzer wrote:
>>
>>> "paul c" <toledobysea_at_ac.ooyah> wrote in message
>>
>> ...
>>
>>>> However, I'm content to say that all three relations have the same
>>>> predicate, assuming no attribute renaming is involved in your
>>>> interpretation. I know many people say that the 'or' is introduced to
>>>> the predicate of R. I don't believe there is any law or principle,
>>>> including relational closure, that requires anybody to think this way.
>>>>
>>>
>>> How can they have the same predicate if they can have different
>>> extensions? That doesn't make any sense.
>>> ...
>>
>> They are misconceived. The example strikes me as akin to Joe C's word
>> games.
>
> To answer Selzer's query, they have different external predicates but the
> same predicate as far as the DBMS can calculate.