As we already know, Kie Sessions come in two different flavors: stateless and stateful. Most of the examples we covered so far involved only stateful Kie Sessions; and there is a good reason why, stateful Kie Sessions are, by far, the most powerful type of sessions supported by Drools.
Before we can decide which kind of session we want to use for a particular situation, we need to understand the differences and similarities between these two type of sessions. In order to do so, we are going to start with the most simple type of session: the stateless Kie Session.
From a development perspective, the type of session we want to use for a particular scenario is not determined by the rules—or any other asset type—we want to use. The type of session is determined either when we define it in the kmodule.xml file or when we programmatically instantiate it in our code. In most of the cases, the same set of assets (.drl files, decision tables...