Re: Guessing?

From: Bob Badour <>
Date: Tue, 08 Jul 2008 12:04:34 -0300
Message-ID: <48738203$0$4049$>

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. Received on Tue Jul 08 2008 - 10:04:34 CDT

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