Re: Oids
Date: Wed, 17 Aug 2005 18:20:24 -0400
Message-ID: <LL-dnWnywtO7JZ7eRVn-tg_at_comcast.com>
"Vadim Tropashko" <vadimtro_invalid_at_yahoo.com> wrote in message
news:1124314917.283480.204740_at_g44g2000cwa.googlegroups.com...
> Summarising:
>
> header(A) = a0 = 00 join A
> rowids(A) = Ox = 00 union A
>
> (Change 'rowids' to 'foo' if you like. Although I find a little comfort
> with informal idea that header can be viewed is an additional hidden
> row in the table, while the list of rowids is an additional hidden
> column).
>
> Now, it seems that you hit the nail, and the rowid maps Relational
> Lattice into a boolean algebra with just 2 elements 00 and 01.
I just faithfully applied your definition of the gen. union. I must admit I was confused by various comments as to how one computes '00' union A until I re-read the article and saw that it was just a union of two projections.
>This is
> dual to header lattice homomorhism of Relational Lattice into a boolean
> algebra of sets. The symmetry is sligtly broken, but who would insist
> that rows and columns are completely symmetrical?
>
Received on Thu Aug 18 2005 - 00:20:24 CEST