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

In message <mn6qb0p2dccituo6m3iklt5j04rml4hjg9_at_4ax.com>, Gene Wirchenko <genew_at_mail.ocis.net> writes
>"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.

Well, is "mass" abstract? Or "energy"?

No they are not. They have formal mathematical definitions within Newtonian Mechanics or relativity, but they also have clear metaphysical descriptions within reality.

As far as I can tell, "relational data" does not have that metaphysical description.
>
>>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.

Basically, Kepler corrected Copernicus' axiom that "orbit == circle"
>
> Newton's is pretty good and will work for everyday situations
>fine. Einstein's refines Newton's to cover yet more cases.

More improvements here :-) The mathematical definition is steadily getting closer to the metaphysical reality ...
>
> 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.

But it doesn't make it correct ...
>
>[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.

It is the closest that YOU 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.
>

Great. So why aren't you prepared to question the accuracy of the axiom that "data comes in tuples".

Yes, relational data DOES come in tuples - because that's what the definition says.

But if you can't come up with some formal way of converting between "real-world-data" and "relational tuples", then surely you have to come to the conclusion (which my and Dawn's EXPERIENCE has forced us to) that your tuple is equivalent to a Copernican circle - it may be close to reality but there's something seriously wrong somewhere that needs correcting - and it CAN'T be done WITHIN the theory, because the fault lies in the theory-to-reality map.

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