- "simple event processing" EPAs - filter and routing,
- "mediated event processing" EPAs - enrichment, transformation, validation
- "Complex event processing" EPAs - pattern detection
- "intelligent event processing" EPAs - prediction, decisions...
The common denominator: each of them receives events as input, emits events as output and does a single type of function.
I find this type of abstraction both very easy to explain people how EP systems work, and also basis for architecture. The EPN routing can be done by standard middleware, or in a stand-alone mode. Other terminology issues raised by David Luckham is the relationships to the "actor model" and to "engines".
The actor model is a model that helps reasoning about concurrency, while agents in AI are autonomous goal-driven artifacts. These are orthogonal terms, of course. In the context of EPA - when looking at EPAs as an executable network, we can look at each EPA as an actor and apply actor models.
Last but not least -- relationships of EPAs to engines -- an EPA is a software artifcat, it can be an instance of an engine, it can be some software that contains an engine, and it can be hard-coded program, as long as it complies with the EPA definition. In a future world, with inter-operability (and perhaps also language) standards, we'll be able to run (and maybe to self-select) multiple engines for the same EPN, residing in different EPAs.
More about EPA types -- later.