Re: By The Dawn's Normal Light

"Laconic2" <laconic2_at_comcast.net> wrote in message news:J_OdnQb_GuO9h-XcRVn-2Q_at_comcast.com... >
> A table represents a set if and only if there is a candidate key.

Saying "at least one" instead of "a" would be less prone to misunderstanding.

> A Relation is in first normal form if and only if none of the domains of its
> attributes permit compound or multivalued values.

This definition is a problem, because it includes two other terms that may themselves be subject to confusion: "compound" and "multivalued."

What do those terms mean to you?

> Now Dawn's objection can be stated as simply as an objection to 1NF, as
> stated. The fact that it's defined in terms of relations makes the no
> duplicate rule unnecessary.

Yes.

> Dawn has mentioned that the difference between Boyce-Codd NF and 4NF is a
> consequence of 1NF. This is confirmed at other websites.

Interesting.

> As to the difference between a list and a table, that is a fairly trivial
> difference. Performance may be different.

That wouldn't be what I'd lead with, especially since the rest of the conversation seems to be working at the logical level.

> Direct access may be different.
> And as Dawn says, "sometimes order matters, sometimes it doesn't" It might
> be nice to have some metadata that tells us whether order matters or not.

Distinguishing between ordered and unordered data is *essential.* Data has meaning; calling unordered data order means imputing meaning to noise; calling ordered data unordered is throwing meaning away.

Marshall Received on Thu Oct 21 2004 - 20:50:59 CDT