Re: Normalization

On Fri, 04 Aug 2000 22:40:52 GMT, Scot A. Becker <scotb_at_inconcept.com> wrote:
>
>Thanks for the kudos. You question, however, is quite tough.

I have noticed that. I did some looking around on the web and saw that both the definitions where used as if they where interchangeable. I even saw an abstract of an article by Date and Fagin that said in the abstract that the two were the same. But maybe they use different definitions, it didn't say in the abstract. Anyway, next monday I am going to the university library and see what I can come up with.

>Your question got me curious, however, so I called around to a couple of
>folks who would know. The responses can be summarized as: "un-important",
>"trivial", and "splitting hairs".

I tried a couple of minutes to prove that PJNF implies 5NF and vice versa, but I didn't find a proof of either implication. So, I don't think it is very trivial :-). And I also think that it is important because it shows that normalization is actually trying to achieve two goals at once: one is removing repeating groups, and the other is to organize the tables in such a way that only key constraints need to be checked. It is easy to see that the 5NF achieves the first goal and that the PJNF attempts to achieve the second goal. So the question that we are talking about is the question if these goals are conflicting or not. Wich is, in my opinion, an important question.

>The paper Halpin cited is: Orlowska, M. & Zhang, Y. 1992, 'Understanding
>fifth normal form (5NF)', Australian Computer Science Communications, vol.
>14, pp. 631-9

Ok. Thank you for the reference, I will see if I can find it.

>I realize that I probably didn't help much, but... I'd say, don't worry
>about it in practice; I suspect the distinction is relevant only to
>relational theory.

Well, this is comp.databases.*theory*, isn't it? :-)

Kind regards,

• Jan Hidders