Re: Distributivity in Tropashko's Lattice Algebra

From: Vadim Tropashko <vadimtro_invalid_at_yahoo.com>
Date: 16 Aug 2005 14:50:45 -0700
Message-ID: <1124229045.121833.237200@g49g2000cwa.googlegroups.com>

Mikito Harakiri wrote:
> vc wrote:
> > What's rowid(A) ?
>
> A set of rowids? This is a dual concept to the relation header: table
> columns are identified by table attribute names, while the rows are
> identified by rowids. Unlike the set algebra of attribute names, the
> algebra of rowids doesn't seem to be boolean.

rowid(A) doesn't appear to be a particularly useful map. If we know rowid(A) and rowid(B), we can't express either

rowid(A join B)

nor

rowid(A union B)

in terms of rowid(A) and rowid(B). Perhaps this explains why the rowid concept has never been popular in database theory? Received on Tue Aug 16 2005 - 16:50:45 CDT