Re: Codd's Information Principle

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.
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Relevant Pages

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    ... But one point seems very immediate to me - for any given relational expression, there is only one equivalent extension. ... 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. ...
    (comp.databases.theory)
  • Re: Codds Information Principle
    ... Bob Badour wrote: ... But one point seems very immediate to me - for any given relational expression, there is only one equivalent extension. ... 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. ...
    (comp.databases.theory)
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    (comp.databases.theory)
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