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

Not everything can be expressed in a formula. Data is an example. You are also confused about the way data is 'chopped up". It isn't. Data has different characteristics depending on its use and the point of view from which one views it (verty much like relativity). Let me try to express this in a way that may be satisfactory to you. It is necessary to do a top-down explanation, I think.

Given a minimum of third normal form:

An instantiated database contains stored information about a miniworld (domain, if you like).

Information is represented by one or more tuples in one or more tables that may or may not be joined to one or more other tables, or itself (a table).

Tables consist of tuples (rows). A tuple represents a piece of complete, bounded, and finite information about the primary key.

The primarty key is a piece of discrete data, as is each attribute (column) in the tuple (row).

Under ideal circumstances, the primary key is a piece of meaningful data from the miniworld (sometimes it is necessary to create an artificial key, but this is still a piece of discrete data. Sometimes the primary key is made up of several attributes (composite key), but this is consistent for each tuple. Although each attribute represents a discrete piece of data, when combined into a composite key, the composite key is also a discrete piece of data, but now contains more information. In chemistry, this would be a "compound" made from several "elements".

Because the Primary Key is unique, and all attributes in a tuple are about that key and nothing but the key, each tuple is complete, bounded, and finite. If the tuple is complete, bounded, and finite, then each element of the tuple (the attributes) must also be complete, bounded, and finite. The attributes themselves do not contain "information" until the tuple is realized.

Knowledge is realized by the examination of all of the information.

So, we have

data is contained in attributes
information is contained in tuples (which are made of attributes) information is also contained in tables, which are really just many tuples knowledge is contained in a database

It's not confusing at all if you don't want it to be.

"Relation" is a term from logical modeling and can be thought of as a "superclass" term that encompasses "entities" and "relationships" and has no place in this argument.

BTW, Time is not the 4th dimension of space. Space is expressed in three dimensions. Time is another dimension for sure, but of something larger that we can't yet identify. For now, we can say that space and time are dimensions of the universe. Space is measured by three dimensions. The universe is measured by the three dimesions of space plus the dimension of time. Of course, there may be more dimensions.

"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message news:JrNFhKFbWRpAFwhL_at_thewolery.demon.co.uk...
> 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
Received on Fri May 14 2004 - 21:47:56 CEST