Minimal Cover

Question

In questions asking for the number of FDs in minimal cover if I get say

A $\rightarrow$ B

A $\rightarrow$ C

D $\rightarrow$ EF

Then what do I count them as

2 or 3 or 4 FDs?

Answer 1

The minimal cover is typically counted by considering the irreducible dependencies. In this case, the minimal cover is:

1. A → B
2. A → C
3. D → E
4. D → F

So, in terms of minimal dependencies, you count them as 4 functional dependencies. The original set you provided had redundancy that was eliminated in the minimal cover.