Re: Application Design and PostgreSQL

On Tue, Jul 17, 2001 at 12:59:09PM +0200, Janning Vygen wrote:
> But then i thought: Do i really need complex middleware or is it just
> a wrapper around PostgreSQL??

Your original thinking is correct.  You want a front-end (client),
some middleware that implements your business logic, and then the
database.

The client should be a basic display/input tool, ideally a browser.
Every computer has one these days.

The middleware is the part that is particularly custom to your
world.  It should be written as portably as possible, for example
Java Servlets in a container such as Tomcat (free) or JRun (not
free).

The communication to the database engine should be only ANSI SQL via
ODBC or JDBC.

By doing this, you will not be at the mercy of any vendor.  You can
swap database engines if desired.  You can play Oracle off against
Informix or Sybase by saying, "It doesn't really matter to me, give
me your best deal."

Every vendor will try to get you to use their proprietary extensions
and/or 4GL.  Be very aware of the hidden costs of such things.  Use
the extensions if it is the =only= way you can build your
application.

We've been through this design cycle several times for some very
large applications, and we've gotten smarter (you might even say
paranoid) about vendor lock-in each time.

> I think its possible to implement the whole logic inside postgresql.

Perhaps.  And if your application is for internal use only, and you
never imagine selling a license version to anyone, and you'll never
get into the ASP business with your app, go for it.

But some day, some pesky customer will say, "Yes, but we've already
got a site license to Informix and a bunch of Informix DBAs so we
won't buy unless it can run on Informix (replace your favorite
annoying commercial database vendor here).  Layer your application
properly and you can say, "We think that would be a mistake, but we
can accomodate your need."

         -crl
--
Chad R. Larson (CRL22)    chad@eldocomp.com
  Eldorado Computing, Inc.   602-604-3100
     5353 North 16th Street, Suite 400
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