Re: OR operator in D&D algebra

From: Vadim Tropashko <vadimtro_invalid_at_yahoo.com>
Date: Fri, 20 Jul 2007 19:18:48 -0700
Message-ID: <1184984328.502132.246550@z24g2000prh.googlegroups.com>

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 Fri Jul 20 2007 - 21:18:48 CDT