How would you position Esper next to existing solutions (or hacks) in the industry?
Esper is the only open source Event Stream Processing out there – and this is not to be confused with classical rules engines. Compared to commercial ESP engines implementations, Esper may lack high availability options in the 1.0 release, but its open source nature is a driver to get the Event processing language right, and get the Java community up to speed on those concepts – before tackling enterprise grade requirements in upcoming versions. Generally Rete-based production rule engines can indeed be used to address part of what CEP coins, especially triggering by correlating events, possibly including a temporal relationship between events. That said the ESP side – Event Stream Processing – is a different beast, where what matters is the “S” for Stream. In this side of the Esper engine we provide several language facilities to build expressions using time not for temporal relationship (happened before etc) but for sliding window. As an example, this makes it very valuable for compu
