Re: Functional dependency is multivalued dependency

Mikito Harakiri wrote:
> The proof of proposition 8.2.2 (page 164, the Alice book) begins with
> observation that given three sets of attributes X, Y and Z such that
> set Z complements sets X an Y in the relation header of the relalation
> I, the pi_XY(I) /\ pi_XZ(I) is always a superset of I. Is it obvious?
>
> In RL we do it in couple of steps:
>
> (XY \/ I) /\ (XZ \/ I) <= I ?
>
> This is the same as
>
> I /\ (XY \/ I) /\ (XZ \/ I) <= I
>
> and the left side reduces to I by 2 applications of the absorption law.
>
>
> That is about prioving the obvious part of the proposition. I'm stuck
> on the non-obvious part. Any ideas?

Do you already know how to represent the FD in RL equations?

• Jan Hidders