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

In message <2gkdtnF3saspU1_at_uni-berlin.de>, Alan <alan_at_erols.com> writes
>From "Fundamentals of Database Systems", Elmasri & Navathe [some direct
>quote, some rephrased for brevity] :
>
>Data: Known facts that can be recorded and have implicit meaning. [direct
>quote]

Nice quote. But I'm being philosophical here. Mass, Energy, and Time are all (from Newton's standpoint) simple, immutable things. Space is as well, although it's slightly different, because it's three orthogonal instances of length.

By these standards, "data" is woefully vague and undefined. And it's not even atomic! Within the theory it's chopped up into tuples, which are themselves chopped up into (I'm not into terminology here) keys, attributes, relations, and probably other stuff besides.
>
>Database: A logically coherent collection of related real-world data
>assembled for a specific purpose. [rephrased]

Given that "data" is so vague, how do we know it's related to the real world?
>
>See? It's not all that complicated. You are applying way too much GRAVITY to
>your question.
>
:-) But I'm looking for the TOE of data.

We know Newton got it wrong. Energy and mass are the same thing. Time is merely a fourth dimension of space. But at least Newton had his philosophical anchors to the real world firmly in place, even if he knew something was wrong.

"data" is not an anchor. It's a formless cloud. One fact may be "object X exists". Another may be "Person A is the mother of Person B". And again, "object Z is blue". Each of those is a different *type* of fact, a different "immutable object". And RDBMS theory lumps them all together in the amorphous philosophical concept of data, and then dismantles them inside the theory, despite the fact that they can't be dismantled in the real world.

Just as we couldn't combine mass and energy and move them inside the theory until we realised that they were interchangeable - e=mc^2 - so we can't move "data" inside relational theory and deal with it there unless we have a rule that can transform one type of data into another. And until we have that rule, we need to treat the different types of data as external to the theory, and have a one-2-one mapping of those with reality.
>

Cheers,
Wol
>
>"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message
>news:o6Qd1REvhApAFwUO_at_thewolery.demon.co.uk...
>> In relational theory, everyone seems to be talking about modelling
>> "data", but I've never seen an explanation of what "data" is. As far as
>> I can tell, C&D took this philosophical concept of "data", and then
>> built their relational theory on top of it. That's okay. We have a
>> (fairly) simple, consistent model. But what the heck IS data?
>>
>> Okay. Let's explain where I'm coming from. You've seen me going on about
>> "evidence" and "science" etc etc. So I'm going to drag science into
>> this, Newtonian Mechanics, to be precise (of course).
>>
>> Newton came up with these philosophical concepts called "mass",
>> "energy", "space" and "time". On these, he built his (fairly) simple
>> consistent model. And then Einstein came along and said he'd got his
>> fundamentals wrong - mass and energy were the same thing, and space and
>> time were the same thing. And because Newton didn't take the fact that
>> these things were interchangeable, his model didn't work when compared
>> to reality.
>>
>> Okay. So what is "data". Because if we can't anchor that in the real
>> world, we have no way of knowing if, or how strongly, relational theory
>> is relevant (and usable) in the real world.
>>
>> 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
>
>

-- 
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