Unlike your normal communication that happens amongst components in an Enterprise system where every message is of importance and is processed, CEP is based on events and there are a very few instances of these event that would be of any importance and would require processing.
Oracle has a Query[CQL] based implementation of CEP where any event of importance is picked from a stream of events using a query and can be processed further.
An example would be a flood alert system across a country propagating continuous stream of events, unless there is no irregular pattern in the events [no flood alert], the events are ignored but on occurrence of an flood[an irregular event] an action can be taken by passing on the information to subsequent processes.
I would recommend this link:
and the book “Oracle soa-suite-11g-handbook” by Lucas Jelema:
Hope this answers your question.