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

"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote:

[snip]

>As for Gene, I agree we need a theory, and actually, I think relational
>theory is a great theory. Unfortunately it is a theory about a - call it
>abstract, call it imaginary, they're the same thing - concept called
>"data" that does not seem to have any basis in the real world.

     That is not surprising since data is abstract.

>So what do I think should replace it? Nothing actually, we can just
>improve it. BUT IN DOING SO, IT WILL BE TRANSFORMED BEYOND RECOGNITION
>:-)

     I do not think so. See further.

>Go back to my analogies :-) In hindsight, we just can't understand why
>the Church couldn't see that Copernicus' theory that the planets orbit
>the sun didn't make sense. Except that *WE* have got Copernicus' theory
>wrong. He thought that the planets *circled* the sun. And as a result
>his theory was just as much as mess (if not more) than that of the
>Church who said the planets and sun orbited the earth. I think *that* is
>the current state of database theory.

     No, the mess was smaller. The new theory was a better theory.

     Newton's is pretty good and will work for everyday situations fine. Einstein's refines Newton's to cover yet more cases.

     The world is nearly flat. The variation from that is a small fraction of an inch per mile. If you are dividing your backyard into plots for gardening, you are safe assuming that the world is flat. When you hit the big time, a different theory is needed. Before then, it is more complicated than you need.

[snip]

>If we can't go - using formal theory - from the database back through
>the analysis to get back to the real world we started from, then we have
>no idea if our axioms are correct, and as Dawn says, we have no idea if
>relational theory is the correct theory to solve real world problems.

     There is meaning that the DBMS understands (for example, FK and RI), and there is meaning that the user understands (and the DBMS does not) such as what a location is.

     A database models relevant portions of the Real World. What does relevant mean? Of interest to someone.

>And as I said before, it we have no idea if it's the correct theory, why
>are we using it? Dawn was going on about faith. Do you have faith in

     It is the closest that we know of.

>business analysts to get the analysis correct, or would you rather have
>a formal, REVERSIBLE and PROVABLE (or testable, falsifiable, scientific,
>whatever term you want to use) logical theory to do it for you?

     I would rather have the theory, but in its absence, I will use what I have.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.