Re: Codd's Information Principle

From: Bob Badour <>
Date: Sun, 01 Nov 2009 18:26:15 -0400
Message-ID: <4aee0b09$0$5320$>

paul c wrote:

> Bob Badour wrote:

>> paul c wrote:

> ...
>>> Didn't mean to suggest otherwise.  Sometimes the immediate expert 
>>> objection to the 'primrose path' turns out to be an advantage if the 
>>> idea is allowed to breath.
>>> But one point seems very immediate to me - for any given relational 
>>> expression, there is only one equivalent extension.
>> I don't follow that at all.

> If you mean the last sentence, I could expand it by saying that for any
> given purpose, in other words any given application, I think that single
> extension must have one interpretation. Since the expression might not
> involve any algebraic operations, I think it is best to discard those in
> the interpretation, no matter how the extension was formed. I say
> 'best' because that seems sufficient to me and I don't see how including
> those ops is necessary. I would like to know what problems this causes,
> eg., I don't see that inconsistences/contradictions or loss of utility
> or inability to optimize result from it.

I cannot make sense of what you wrote. Received on Sun Nov 01 2009 - 23:26:15 CET

Original text of this message