Re: You have ... business rules & 3tier

I'm a little confused about "business rule engine" and "application server".

Currently, I view an application server as a way to avoid a client-side upgrade of software and a central place for delivering and receiving messages. For example, changing a plsql cartridge application in OAS is easier than sending the client a new piece of software and OAS provides a central resource for sending and receiving messages between client and database.

A business rule, I think, can be something static like "an xyz object has an x component, a y component and a z component". Or something more dynamic like "if the x component is 100 then the y component is 200 times the z component otherwise y can be positive number. " Or something derived such as "the Q factor is (x+y)*z". I suspect that these three rules can be implemented as a database table with three fields, an insert and update trigger on the table and a packaged function.

The application server may deliver messages about the valid business rules to the client (what fields can have input values, the limitation on y and the function that computes Q), so that client-side input and checking can be done, but where does the "business rule engine" fit in this?

Specifically, in OAS how does one build a business rule engine and what does it do besides delivering messages about the structure of the database?

Frank Hubeny

Jonathan Lewis wrote:

> In a correct 3-tier design there is arguably
> only ONE application EVER that touches
> the database, and that is the business
> rule engine in the application server.
Received on Sat Mar 18 2000 - 00:00:00 CST