Re: Functional dependency is multivalued dependency
From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 29 Apr 2006 15:17:14 GMT
Message-ID: <_rL4g.87971$P01.66258_at_pd7tw3no>
Date: Sat, 29 Apr 2006 15:17:14 GMT
Message-ID: <_rL4g.87971$P01.66258_at_pd7tw3no>
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 ?
> ...