Re: Codd's Information Principle
Date: Sun, 01 Nov 2009 22:21:21 GMT
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 - 23:21:21 CET