CLIPS is a programming language for writing expert system shells.
It resembles LISP but is generally geared to forming rules (condition-action pairs) and holding a fact base that the rules manipulate.
CLIPS was invented by NASA based on the OPS-5 expert systems language.
CLIPS uses a form of rule evaluation called forward-chaining. It finds facts by implication, rather than by deduction -- which is how PrologLanguage does it.
CLIPS is generally regarded as an artificial intelligence programming language.
There is a commercially available Java implementation of a CLIPS dialect called "Jess". It was created by Sandia Labs and is available for licensing from them.