Re: Newbie question about db normalization theory: redundant keys OK?

From: Frank Hamersley <>
Date: Sat, 22 Dec 2007 11:07:22 GMT
Message-ID: <Kd6bj.26430$>

David Cressey wrote:
> "Brian Selzer" <> wrote in message

> The question arises whether the database communicates any data other than
> the data contained in its state. I'm going to pull a quote from Codd's 1970
> paper. Even though this quote is about consistency, rather than identity,
> I want to draw your attention to the wording.
> "It is important to note that consistency as defined above
> is a property of the instantaneous state of a data bank, and
> is independent of how that state came about. Thus, in
> particular, there is no distinction made on the basis of
> whether a user generated an inconsistency due to an act of
> omission or an act of commission. "

Interesting - I had always assumed that Codds use of "time varying" had implied temporality but the above quote must weaken that view.


> It seems to me that, if you are going to assert that the history of a
> database is part of the interpretation of its content, it's going to be up
> to you to explain how a database can serve up any relevant portions of its
> own history as data.

Many have tried! AFAIK all have failed.

Cheers Frank. Received on Sat Dec 22 2007 - 12:07:22 CET

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