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

"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message news:DRon$bDW46vAFwij_at_thewolery.demon.co.uk...
> In message <ckHvc.10429$wI4.1251077_at_wards.force9.net>, Paul
> <paul_at_test.com> writes
> >> I'm not sure a database is a finite set of axioms.
> >
> >Why not? A databases is just a finite set of tuples from which you
> >derive other truths.
>
> In which case, your database is arbitrarily complex ...
>
> The whole point of axioms is that YOU DON'T WANT THEM! The aim of
> logicians, mathematicians, and scientists is always to simplify things.
> If you can derive an axiom from other axioms, it ceases to be an axiom
> and becomes a theorem, and makes your fundamental theory simpler.
>
> To define "axiom == tuple" is, I think, a major mistake. I can't explain
> why, it just feels COMPLETELY wrong.

Fine - so do you propose a data theory that requires no axioms?

> >> And the set of facts in a database can grow arbitrary large
> >> (theoretically speaking).
> >
> >There's a big (though maybe subtle) difference between "infinite" and
> >"unbounded but finite". Even though there is no theoretical limit to
> >the size of a database, we do know that any given database is of finite
> >size.
> >
> Yep. But as any scientist will tell you, an unbounded axiom set is a
> crap theory. That's why it feels wrong.

I don't equate tuples with axioms, at least not as far as a theory like relational goes. I'm out of my depth in terms of the logical lexicon, but I'd say predicates correspond better, and if you have an unbounded predicate set, then yes, you've got crap.

And in addition, if tuples are axioms, then they're not unbounded; each must match its designated predicate, which places bounds. Depending on the types of your attributes, you could have an infinite number... so it comes down to the degree of unboundedness. Using predicates limits the cardinality.

• erk