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Re: Base Normal Form

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Mon, 04 Jul 2005 19:41:12 GMT
Message-ID: <shgye.137258$4T6.7275581@phobos.telenet-ops.be>


David Cressey wrote:
> I'd like to suggest a new Normal Form definition, one that I'm calling Base
> Normal Form, for lack of a better term.

In some texts I've seen it called the UNF (unnormalized normal form) or the NFNF (non first normal form). To make things confusing, it is also equivalent with Chris Date's definition of 1NF.

> I haven't defined candidate key, but I would want the definition to be
> compatible with the definition of candidate key as used in BCNF.

That's do-able. If you define a table as a list of tuples that all have the same attributes, then a superkey is a set of attributes K such that there cannot be two different positions in the table such that the tuples at these positions agree on the values for K. The notion of candidate key is then based on the notion of superkey in the usual way.

Note that this definition is sloppy in the usual way where we ignore the fact that a candidate key is not so much a property of a single relation but rather of the set of all relations that are valid for a certain relvar.

> I'm speculating that this definition, together with BCNF, would be
> sufficient to cover introductory DB design, skipping over 1NF, 2NF, and 3NF,
> and leaving normal forms beyond BCNF for more advanced treatement.

I wouldn't skip 3NF. The difference between BCNF and 3NF is an important one and the decision to go beyond 3NF should be an informed one.

Received on Mon Jul 04 2005 - 14:41:12 CDT

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