Jess is a rules engine with excellent Java interplay. "Jess in Action" is a fast and swift read. Actually using Jess is surprisingly difficult.



In "Jess in Action", you will read about the Jess syntax (facts and rules), how it interplays with Java (scripting Java from Jess, Java Beans as shadow facts, calling Jess from Java) and very extensive examples with very detailed backgrounds.



All for version 61p4. The current Jess version is 71p2. As a bonus one can download from the books website a nonprofit version of Jess without a time limit. Unfortunately: Jess is not open source.



If you want to do some Jess, "Jess in Action" is an excellent complement for the online documentation.