Database Design and Relational Theory: Normal Forms and All That Jazz

© C. J. Date 2019

C. J. DateDatabase Design and Relational Theoryhttps://doi.org/10.1007/978-1-4842-5540-7_7

7. FD Axiomatization

C. J. Date¹ 

(1)

Healdsburg, California, USA

 

[The] true and solid living axioms

—Francis Bacon: The New Organon (1620)

I’ve touched on the point several times already that some FDs imply others; now it’s time to get more specific. First of all, however, I need to introduce some notation—notation that (a) reduces the number of keystrokes required in formal proofs and the like and (b) can also help, sometimes, to see the forest as well as the trees, as it were.

As you might recall, Heath’s Theorem as I stated it in Chapter 5 included the following sentence: Let XY denote the union of X and Y, and similarly for XZ. The notation ...