Re: "Armstrong's axioms" augmentation - help plz
From: paul c <toledobythesea_at_oohay.moc>
Date: Mon, 07 Mar 2005 18:23:23 GMT
Message-ID: <v_0Xd.595298$Xk.317716_at_pd7tw3no>
Date: Mon, 07 Mar 2005 18:23:23 GMT
Message-ID: <v_0Xd.595298$Xk.317716_at_pd7tw3no>
love boat via DBMonster.com wrote:
> I understand the Augmentation rule:
> { X -> Y } |= XZ -> YZ
>
> but I don't understand why the rule can also be stated as:
>
> { X -> Y } |= XZ -> Y
>
> Why is this?
>
- YZ -> Y (reflexivity)
- XZ -> YZ (given)
- XZ -> Y (transitivity)
finally, a question i can answer,
p
Received on Mon Mar 07 2005 - 19:23:23 CET