Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> comp.databases.theory -> Re: completeness of the relational lattice

Re: completeness of the relational lattice

From: Vadim Tropashko <vadimtro_invalid_at_yahoo.com>
Date: Tue, 26 Jun 2007 14:31:21 -0700
Message-ID: <1182893481.352583.84760@e9g2000prf.googlegroups.com>


On Jun 26, 1:48 pm, Jan Hidders <hidd..._at_gmail.com> wrote:

>           (R(x,y) * []) + (R(x,y) * W)

> (22) = [x,y] + (R(x,y) * W)
> (9) = ([x,y] + R(x,y)) * ([x,y] + W)
> (10) = R(x,y) * ([x,y] + W)
> (11) = R(x,y) * (([x] * [y]) + W)
> (9) = R(x,y) * (([x] + W) * ([y] + W))
> (32b) = R(x,y) * <x> * <y>
> (28) = R(x,y)

I don't think the axiom #9 (as written in one of your previous posts) is correct. First, it should be more restrictive than #8 and it looks less restrictive. Anyway, the first application of distributivity is correct. I doubt the second one. In the distributive law:

A + (B*C) = (A+B) * (A+C)

the attributes of B are required to be a superset of A, not subset. Received on Tue Jun 26 2007 - 16:31:21 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US