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Re: TRUE and FALSE values in the relational lattice

From: David Cressey <cressey73_at_verizon.net>
Date: Thu, 21 Jun 2007 18:39:33 GMT
Message-ID: <FBzei.10694$015.9828@trndny05>

"Vadim Tropashko" <vadimtro_invalid_at_yahoo.com> wrote in message news:1182446779.883211.130730_at_e9g2000prf.googlegroups.com...
> On Jun 21, 3:14 am, Jan Hidders <hidd..._at_gmail.com> wrote:
> > I would assume the following operations: (in yet another notation)
> > - E * E : natural join
> > - E + E : generalized union
>
> Eh, 3 different people, 3 different notations:-)
>
> > - {()} : the relation with empty header and a single empty tuple
>
> OK
>
> > - [A,B,..D] : the empty relation with header {A, B, ..., D} (possibly
> > the empty set)
>
> This is nice proposal. How abotut small letters for attributes and
> capital letters for relations?
>

Why not the following?

{A,B,..D ()} Received on Thu Jun 21 2007 - 13:39:33 CDT

Original text of this message

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