Re: Data Layer architecture

Alfredo Novoa wrote:

> On Sun, 24 Jul 2005 11:53:09 +0200, "Wessel Troost"
> <nothing@xxxxxxxxxxxx> wrote:
> > On a next project, I used only two layers and dropped the message
> > queues. Development speed was amazing. We were responsive to the
> > customer's requests, and able to deliver on time.
> >
> > A good learning experience though.
>
> But it is a very expensive learning way. Everyone with a clue on data
> management theory knows that the business logic must be ensured by the
> DBMS and not by the applications (this is taught in the first week of
> any serious database course).

Hmm, then my serious db courses at the uni weren't very 'serious'
then!

NO law states that BL has to be IN the DBMS.

BL is a data-consuming tier, not part of the relational model. If you
pick up a book by Nijssen or Halpin, or Yourdon for that matter, you'll
learn that relational theory, e.g. the schema setup in your DBMS, is
not a theory which states anything about business rules. It only gives
context to the data its format it defines, no logic whatsoever.

> Applications must be the presentation layer of an Information System
> (something known since the 60's), and we should keep away from all the
> business objects trade media garbage.

One researcher once made a list of how many client-server
architectures there were, he came to 7 if I'm not mistaken. Your
proposed setup is one of them, but far from the only one.

What you suggest is typically a big-iron box in the basement, and thin
clients connecting to it, where all the software is written by DBA's.

I hope I don't have to drop the word 'scalability' on you.

FB

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