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

In message <u%%vc.5733$1I.4192_at_newssvr32.news.prodigy.com>, Eric Kaun <ekaun_at_yahoo.com> writes
>> By George, you've got it., Wol!!! Perfect!
>>
>> Relational theory, once some choice axioms are added in (without being
>> stated as axioms and without being obvious that they out to be axiomatic
>> when measured by any map to reality) does then proceed with mathematics,
>but
>> there is a lot of "tossing stuff in and out" going on because there is not
>> that match with reality at each point.
>
>So what mathematical axioms do you know of that "map to reality"? I didn't
>realize that was the fundamental aspect of an axiom's value. And if it is,
>then again, what data axioms do you propose as a good start? They needn't be
>formal, but have to have more meaning than "data comes in tuples".

e=mc^2 ?

Yep. I know it's bl**dy difficult. But if you're not prepared to attempt it, then you're admitting your theory is irrelevant to the real world (and cannot be used to solve real-world problems).

Let's take the evolution of that theory I keep on throwing out as an example.

Copernicus : orbit == circle
Kepler : obit == ellipse
Newton : F=ma; E=1/2mv^2 where m is constant Einstein : e=mc^2

Each change may only subtly modify the previous axioms, but the result is theory/model that is a closer fit to reality.

Going back to relational theory. Does the THEORY distinguish between a "join" and a "join with a cascading delete"? Or a "join" and a "join with a foreign key that must exist (cannot be null)".

Because if relational theory cannot cope with that, then the Pick model can. And surely, a relational table who's rows are meaningful in their own right MUST be different from a table who's rows are meaningless without another table to relate to?

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