It's great to see the world finally rediscovering this stuff. CEP is a superb paradigm that makes reasoning about so many kinds of complex, asynchronous systems far easier. One just has to get over any aversion to storing a massive event store. The good news is that great datastores exist for this purpose and one can usually bootstrap by storing events in whatever relational DB you are already using until size/perf becomes an issue.

This is great article. I really like the work from Stanford on Rapide (a declarative, logic style language for event pattern rules).

http://complexevents.com/stanford/rapide/

The site is a bit outdated but the language is awesome.

Also check out these books on CEP:

http://www.amazon.com/Power-Events-Introduction-Processing-D...

and

http://www.amazon.com/Event-Processing-Action-Opher-Etzion/d...