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

"Cimode" <cimode_at_hotmail.com> wrote in message news:1177951432.567456.276000_at_u30g2000hsc.googlegroups.com...
> 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.
>

My interpretation is not subjective. It may not be precise--I'm often guilty of that, but it is not subjective. In "Extending the Database Relational Model to Capture More Meaning," December, 1979, Codd describes the difference between the open world interpretation and the closed world interpretation in the following way: "One may choose to interpret the absence of an admissible tuple from a base relation as a statement that the truth value of the corresponding atomic formula is (1) unknown; (2) false. If (1) is adopted, we have the open world interpretation. If (2) is adopted, we have the closed world interpretation" He then goes on to say, "Whether the open or closed interpretation is adopted, the relational model is closely related to predicate logic."

I stand by my statement: in a closed world, there is no such thing as "missing information." If a tuple contains a null for one of its attributes, then the truth value of its corresponding atomic formula is unknown. Consequently, in a closed world, the tuple simply could not exist. Received on Tue May 01 2007 - 04:49:11 CEST