I have been using Esper in the last 2 years to solve several problems requiring near real time latency with the same technologies uses in this article.From DSL router events to Business Activity Monitoring.The fact that you can go to production with the Open Source version is awesome and the community is really helpfull.
Wow, that's incredibly simple! We've been looking at using ESPER at work to do correlative analysis and aggregation on telephony events that go through our system, but figured the configuration of that system would be fairly complex.
This is an incredible little demo of JRuby and ESPER, and shows how simple it can be to get up and running! I can't wait to show this to everyone and get a dev spike going.
Look at active database research from the 90's. They all had event languages like this. My PhD research was in developing a domain independent event query language (EQL) that was very similar. This was 12 years ago.