Jess Inventor Opines About Rule Engines and Java "Jess is designed from the ground up for integration, and in Jess 7.0 it's going to get even better. Current versions of Jess can only reason about data in its own working memory (although you can use backward chaining to fetch data into working memory as needed.). Jess 7.0 is going to have the ability to reason about data that isn't in working memory, making it possible to efficiently make inferences about truly huge data sets.
Jess has been integrated with agent frameworks and other tools. It's also been integrated with the popular ontology editor Protégé 2000. This is a powerful combination that many people use to develop knowledge structures as well as code that acts on them...Third-party translators between Jess and RuleML and Jess and DAML exist. One of the features planned for Charlemagne (Jess 7.0) is native XML support."