Drools 5.0 now supports CEP and workflows. I did not get to checkout the workflow support yet, but CEP using rules is a topic I have been involved while at the extreme Lab @ IU. Although it is not apparent, CEP network (different compositions of event streams) and the Rete algorithm, which is the underline algorithm for Drools, both share much in the sense that both construct a tree to represent queries and match events by propagating them through the tree. We worked on creating a layer on top of Drools to handle CEP, but by supporting events from Drools deep down, Drools have enabled concurrent processing, whereas the layer we build on top of Drools have to be synchronized because Drools is not thread safe. It is going to be a versatile tool to build new applications/ usecases.