Jess is a fast, light rule engine and scripting environment written entirely in Java. You can build Java software that has the capacity to "reason" using knowledge you supply in the form of declarative rules. It is supplied as a programmer's library, making it ideal for embedding in larger applications. Jess includes development tools built on the Eclipse platform. It is free for academic use and can be licensed for commercial use.
The major new feature in this release is "peering". Any number of Jess instances can now share a single rule base, leading to much faster startup and reduced memory usage for systems in which multiple engines run the same rules on differing data.
URL: Jess, the Rule Engine for Real Programmers