Re: OR operator in D&D algebra

On Jul 20, 6:51 pm, Vadim Tropashko <vadimtro_inva..._at_yahoo.com> wrote:
> With such an equivalence RA projection is again is defined as a union,
> for example:
>
> project(x) R(x,y) = [x] <OR> R
>

...except that there is no way to express the empty relation [x] anyhow, because it is equivalent to the empty set.

So the question is then if we can express projection in an arbitrary boolean algebra via canonic BA operations? Received on Sat Jul 21 2007 - 04:18:48 CEST