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If there is a universal truth about applications, it is that business rules will change over time. The criteria used to apply a discount, or even the amount of the discount itself, we are using today will—without any doubt—have to be modified tomorrow. We, as the architects and developers of these applications, have to be prepared for this.

Drools provides us with a way to mitigate this issue already. The separation that Drools introduces between the applications and the business logic allows us to decouple the changes happening in the business logic—which are usually frequent—from the changes happening in the application's infrastructure or UI, which are not so frequent.

Regardless of all the advantages provided by this separation, there is still one major problem that remains: every time our business logic (rules) changes, any KieContainer that referenced it has to be notified.

We already saw how a KieContainer can be manually updated when a new version of a KieModule is deployed...