Re: In an RDBMS, what does "Data" mean?
Date: Wed, 2 Jun 2004 12:12:53 -0500
"Eric Kaun" <ekaun_at_yahoo.com> wrote in message
> "Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message
> > And the problem I have is that I cannot see any metaphysical interface
> > between reality and relational theory. This is basically Dawn's point
> > about "is relational theory even the right theory to use?".
> > 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.
> > 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
> > :-)
> So what improvements would you make? From what I've heard suggested
> elsewhere, it's not a transformation beyond recognition.
> > What we NEED is a "theory of business analysis" - a formal theory that
> > tells analysts how to analyse the real world.
> Oh... you're serious?
> > And I'm pretty damn
> > confident that you can NOT create a theory that will do a reversible
> > mapping between the real world and relational data.
I agree and figure that we will have a useful theory of this sort when we have the same on "how to parent a teenager". However, in some ways, Wol is making a similar argument to mountain man (even if they might not agree with that) in identifying that even if relational theory were good to apply, it is useful in a rather small portion of what we do in addressing the "data processing" needs of a business.
> So what precisely is different about other theories of data that do allow
> reversible mapping? And are there properties other then reversibility that
> are desirable in such a model?
> > This theory will then be the equivalent of Kepler and Newton discovering
> > ellipses and calculus, or of Einstein realising that mass and energy
> > were interchangeable. Basically, pretty much ALL of relational theory's
> > axioms are taken as given by the mathematicians, and no thought is given
> > as to whether they actually match the real world.
> Which axioms don't match? I wasn't really aware there were axioms per se.
There are at least the axioms of set theory and then some things were tossed in the mixed without any proof from these axioms, such as restricting the sets from which elements can come to sets of scalar values (which has been changed now, but 1NF, however defined, would have to be considered an axiom since it does not arise from any other mathematics)
> > To give you a simple example, the business analyst analyses an invoice,
> > and you design the database to store the data. Can you then ask the
> > DATABASE to give you the invoice data back?
> > Certainly with current
> > relational databases accessed with SQL, you're relying on either an
> > application programmed OVER the database, or a view which gives you
> > multiple copies of data of which the original only had one.
It think it is worth noting that is far more difficult to retrieve an invoice the way it looked originally after chopping it up (that 1NF thing again) and then using SQL to show the invoice again. It is possible, however, so perhaps Wol has looked at some more difficult specimens. Loosely stated - SQL can only place on a single line entities that are related to each other on that one line. Stick with me here, I know I said that poorly.
Qty....Item..........................Catalogs.............................Co lor.............Price 1 Beautiful Skirt Summer Collection. White $120.00 2004 Wardrobe Catalog. Blue
Without arguing the semantics (and mapping of the data to reality) of this particular example, if your invoice looked like this when selling a beautiful skirt in white and blue that comes from two of your catalogs, it is definitely HARDER than a non-1NF environment, though not impossible, to get a SQL statement to show your invoice properly.
> > Yes I know people are likely to say that "SQL is not genuine
> > relational", but you're still relying on a view - even a valid
> > relational one - or an application.
> So what do you want - the invoice paper? Maybe we should just rely on
> scanners producing JPGs - non-lossy, of course.
No need -- including lists in your data (at least your virtual data!) gets you far enough that you don't notice any more big disconnects. SQL Server permits lists in their UDFs, while Oracle (to my knowledge) does not allow lists returned from their functions (stored procedures)
> > 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.
> Most real-world problems are more than just round-trip regurgitation.
> any trivial serialization scheme fits that bill?
> > And as I said before, it we have no idea if it's the correct theory, why
> > are we using it?
> So what do we have that's correct? You mean the round-trip is your litmus
> > Dawn was going on about faith. Do you have faith in
> > 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?
> Sure. I also want to fly, eat infinite amounts of ice cream without
> weight, and drive at very fast speeds with no possibility of injury.
As long as we are all aiming for the same things ... smiles. --dawn Received on Wed Jun 02 2004 - 19:12:53 CEST