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Re: You have my sympathies

From: Nuno Souto <nsouto_at_nsw.bigpond.net.au.nospam>
Date: Wed, 15 Mar 2000 08:35:16 GMT
Message-ID: <38cf446d.3089705@news-server>


On Wed, 15 Mar 2000 07:41:38 -0000, "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote:

>
>Whilst I am a strong believer in
>database-enforced integrity, I
>would like to throw out the following
>thought;

I hear you.

>
>In the current Nirvana of 3-tier architecture
>we have as the three layer of the system
>(adjust names to suit your favourite terminology)
>
> presentation
> business rules
> data server
>
>Now, the fact that an order can only be
>placed by an existing customer is a
>business rule, is the responsibility
>of the middle tier.

You forgot one very important element. Mentioned it at the beginning, but then got lost. Data Integrity. It belongs in the database server, not in the application server.

The business rule says: an order must be placed by an existing customer. It probably also says that an order is made up of a number of steps and elements. Fine. Put the data integrity bit where it belongs and code the fiddly "elements and steps" in the application.

Don't forget that application servers in the 3-tier model were initially thought out because it was hard to distribute and maintain all that code in all the clients. Nothing is/was said about data integrity and business rules. Of course, this 3-tier concept was "grabbed" and "bent" by designers who didn't know better, hence the situation we see now.

>
>(My personal theory on this one is that
>theory is grand, but belts and braces means
>you don't lose your trousers).
>
>

Amen!

Cheers
Nuno Souto
nsouto_at_nsw.bigpond.net.au.nospam
http://www.users.bigpond.net.au/the_Den/index.html Received on Wed Mar 15 2000 - 02:35:16 CST

Original text of this message

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