Re: Codd's Information Principle

From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 01 Nov 2009 22:21:21 GMT
Message-ID: <BRnHm.51127$PH1.46245_at_edtnps82>

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. Received on Sun Nov 01 2009 - 16:21:21 CST