Re: A new proof of the superiority of set oriented approaches: numerical/time serie linear interpolation

On 30 avr, 18:08, "Brian Selzer" <b..._at_selzer-software.com> wrote:
> "Cimode" <cim..._at_hotmail.com> wrote in message
>
> news:1177938789.949723.62480_at_h2g2000hsg.googlegroups.com...
> [snip]
>
> > I am aware of that article but thank you for reminding it. It simply
> > a negation of previous work and has been demonstrated since as wrong
> > by Codd's disciples (Date, Darwen). The induction of NULL 3VL simply
> > breaks the POCW (Principle of Closed World) redefining the meaning of
> > a database as a collection of facts. I think of this tolerance as one
> > of Codd's errors.
>
> In a closed world, there is no such thing as "missing information." Can you
> provide a reference that states that Codd adopted the closed world
> assumption? I've never read that he did, and in light of his views on
> missing information, I would be surprised if he had. In an open world, the
> focus is on what has been stated, and the contents of a database is a
> collection of recorded facts, not a collection of all of the facts. D&D's
> interpretation of the RM differs from Codd's in several substantive ways.
> Aside from missing information, Codd never described a database as a
> collection of relvars. In everything I've read, he has always referred to
> database modifications as inserts, updates and deletes. This would follow,
> since inserts, updates and deletes are statements that specify how what is
> known about the universe now differs from what has already been recorded.
> D&D's interpretation posits that insert, update and delete are simply
> instances of relational assignment, blissfully ignoring their inherent
> dependency on the current state.
The closed world is a precise concept identified by Date as a consequence of RM 2VL. It is not just a figure of speech open for subjective interpretation or redefinition. The closed world assumption basically states that any proposition that can not be validated by TRUE (existing tuple) should necessarily be validated by FALSE(non existing tuple). The induction of a 3VL through NULL simply breaks that principle because once neither can validate the proposition by TRUE for existing tuples nor one can invalidate the proposition for non existing records.

Hope this clarifies. Received on Mon Apr 30 2007 - 18:43:52 CEST