Re: Checking a relation in BCNF for MVDs

From: Sebastian <space_cadet_at_gmx.de>
Date: 12 Jan 2003 14:50:14 -0800
Message-ID: <c0b511e1.0301121450.36a4f5a@posting.google.com>

Hi,

> A relation is in 4NF if for all non-trivial MVDs X->>Y the set X is a
> superkey.

This definition makes perfect sense to me now that I read a lot about 4NF and compared various definitions. Anyway, our coursework is finished by now, and I think we've done a good job (IN SPITE of Conolly!).

> and as a small reminder:
>
> An MVD X->>Y is trivial if and only if X + Y contains all attributes of the
> relation.

Hmm, don't want to be a smartass, but I remember reading somewhere that when X = Y, it is trivial as well!

> Whether a combination is a foreign key or not is not relevant for
> normalization because it only deals with what happens inside a relation.

Makes sense. Thank you for the help. I love newsgroups!

-seb Received on Sun Jan 12 2003 - 16:50:14 CST