Re: foreign key constraint versus referential integrity constraint

"Tegiri Nenashi" <tegirinenashi_at_gmail.com> wrote in message news:84d21c7e-c6df-48a3-b5c9-f012caeded08_at_12g2000pri.googlegroups.com...
> On Oct 25, 11:06 pm, "Mr. Scott" <do_not_re..._at_noone.com> wrote:
> > I think we should make the distinction, and formally.
> >
> > (p /\ q) -> r is not the same as (p -> r) /\ (q -> r)
> > but (p \/ q) -> r is the same as (p -> r) \/ (q -> r)

> I don't follow. If these are BA expressions with the "->" as material
> implication, then
>
> (p v q) -> r = ~(p v q) v r = (~p ^ ~q) v r
> (p -> r) v (q -> r) = (~p v r) v (~q v r) = (~p v ~q) v r
>
> If the "->" is interpreted as deduction symbol (that is partial
> boolean lattice order), then
>
> (p v q) < r is not the same as (p < r) or (q < r)

You're right.

(p /\ q) -> r is not the same as (p -> r) /\ (q -> r) but (p \/ q) -> r is. Received on Mon Oct 26 2009 - 20:01:43 CET