Love Drools. The consultancy I worked for made so many happy customers by just simplifying a lot of complex optimization use cases with Drools. Hard to do better than Drools for rule-based anything if you’re on the JVM.

Ok… I know how this sounds, but… have you considered changing the name? I, too, like Drools a lot, but seriously, the looks when I tell a bunch of stuffy MBAs that we’re going to manage the complex rules using a tool called “Drools”…

Try pronouncing it "D-rules".

As someone who is only recently getting into rules system development, outside of the manual, are there any other great references you would recommend for understanding rules systems like modern Drools?

You might find the CLIPS docs useful [0]. iirc, DROOLS was at least in part inspired by CLIPS. Plus the CLIPS docs are very well written as noted elsewhere.

The book "Expert Systems: Principles and Programming" [1] is also good though now out of print.

[0] http://www.clipsrules.net/Documentation.html [1] http://www.amazon.com/exec/obidos/tg/detail/-/0534384471/ref...

Pyke [1], a Python based rules engine, supports both forward and backwards chaining. The docs are good. We used it in an AI class I was a TA for; the previous years used Prolog and everyone (most everyone) consistently hated Prolog.... For students used to the video games that are IDEs these days, SWI Prolog and its UI is awful. Pyke and PyKnow were well received, however. As it is Python based, it is a lot easier to deal with than Prolog.

[1] http://pyke.sourceforge.net/index.html

Thank you for this! I was looking for a similar tool and glad I discovered Drools.