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

In message <JMZsc.8405$NK4.1002961_at_stones.force9.net>, Paul <paul_at_test.com> writes
>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.

So if you use Newtonian Mechanics to prove where Mercury was 400 years ago, your proof is more accurate than Tycho Brahe's observations - which place it somewhere else?

You are making exactly the mistake that made me start this thread - you are assuming that the DBMS *defines* reality, rather than carrying out experiments to show that the DBMS accurately *describes* reality.

What you should have said is "IF the dbms is an accurate model of real life then ...". Which is basically what I said - if the dbms and real life disagree then the dbms model must be wrong. You seem to be saying that it's reality that's wrong ...

The problem I have is that the mathematicians seem to have taken C&D's idea of "data" and built this wonderful theory on top of it. Unfortunately, what they have not done is to define "data" in real-world terms (rather than mathematical), and as such there is no way we can go from a "proof within the model" to a formal description of the reality that that proof represents. So you can come up with all the proofs you like within the dbms, but you cannot show that the equivalent real-life scenario is true because you cannot describe that scenario accurately. So by definition the theory is unscientific because you cannot show that the dbms proof is true (or false) in real life.

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999