Re: In an RDBMS, what does "Data" mean?

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"Paul" <paul_at_test.com> wrote in message news:JMZsc.8405$NK4.1002961_at_stones.force9.net...
> Anthony W. Youngman wrote:
> >> So I guess the applicability of databases here is that your relations
> >> are the axioms of your "theory". Your real-world interpretations of
> >> those relations are your "models" of the theory. And the Completeness
> >> Theorem assures you that everything you expect to be true in the real
> >> world will in fact be provable by the DBMS.
> >
> > And if they turn out to be false in the real world and provable in the
> > DBMS, then the DBMS theory is wrong ... (or the DBMS predicts something
> > is false when it turns out to be true ...)
>
> Well, the Completeness Theorem has a converse called the Soundness
> Theorem (http://en.wikipedia.org/wiki/Soundness_theorem), which assures
> us that first order logic is consistent. i.e. everything that you can
> prove in the DBMS is true in real life. This was known long before the
> Completeness Theorem I think, and is easier to prove.
>
> > Or if you can't prove it in the DBMS, then the theory is incomplete ...
>
> The Completeness Theorem proves the "complete" part. i.e. everything
> that is true in all models or interpretations of the database will be
> provable by the DBMS.

Is something that is true in only one model provable by the DBMS ? What this "all models" thing has to do with databases ? Just one model wouldn't be enough ?

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