Re: Universal Quantifier
From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 27 Jan 2007 15:55:23 GMT
Message-ID: <LBKuh.812903$5R2.243620_at_pd7urf3no>
>
>
> Faking it heavily, I suggest something along the lines of:
>
> forall A1(p1,q1) in A(p,q). forall A2(p2,q2) in A(p,q).
> if p1 = p2 then q1 = q2;
>
> where p is actually the set of attributes composing the key and q is
> actually the set of dependent attributes.
>
> One also has to express irreducibility, though.
Date: Sat, 27 Jan 2007 15:55:23 GMT
Message-ID: <LBKuh.812903$5R2.243620_at_pd7urf3no>
Bob Badour wrote:
> ...
>> What formula would express a primary key?
>
>
> Faking it heavily, I suggest something along the lines of:
>
> forall A1(p1,q1) in A(p,q). forall A2(p2,q2) in A(p,q).
> if p1 = p2 then q1 = q2;
>
> where p is actually the set of attributes composing the key and q is
> actually the set of dependent attributes.
>
> One also has to express irreducibility, though.
p Received on Sat Jan 27 2007 - 16:55:23 CET