Jess (programming language)

Jess is a rule engine for the Java platform that was developed by Ernest Friedman-Hill of Sandia National Labs. It is a superset of the CLIPS programming language. It was first written in late 1995. The language provides rule-based programming for the automation of an expert system, and is frequently termed as an expert system shell. In recent years, intelligent agent systems have also developed, which depend on a similar capability.

Rather than a procedural paradigm, where a single program has a loop that is activated only one time, the declarative paradigm used by Jess continuously applies a collection of rules to a collection of facts by a process called pattern matching. Rules can modify the collection of facts, or they can execute any Java code. It uses the Rete algorithm to execute rules.