In this chapter, we saw an overview of the different type of sessions that Drools supports and their advantages and disadvantages. Knowing the available type of sessions will allow us to take better decisions when implementing our solutions with Drools.

We also covered the common patterns of interactions between Drools and our applications. The way how global variables, channels, and queries can be used to extract or provide information to Drools was also explained in great detail. When and what is needed for getting information on what is going on inside Drools internals, we now know that we have a powerful mechanism in our hands by using event listeners.

The last part of this chapter focused on the different ways to enhance and customize the DRL language to create more readable and maintainable rules.

It is time now to move to another important topic in Drools that deals with temporal reasoning inside a Kie Session: Complex Event Processing.