... or Drools, or the Jena Rules Engine (beautiful source code and easy to modify), or http://www.clara-rules.org/

I really appreciate how rules engines can deal with asynchony: they're great for systems where you apply for a loan online but the loan officer has to look at the application. I wrote a data processing toolkit that wrote a set of production rules for Jena that would build and tear down flux pipelines to do... just about anything. Would love to see production rules applied to the async comm problem on the front end.