JanusA concurrent constraints programming language.
From the jc Home Page (see below):
Janus is an instance of a concurrent constraints programming language due to Saraswat et al.: these languages are an elegant generalization of concurrent logic programming languages and constraint logic programming languages. The computational paradigm is one where a set of concurrently executing agents interact with each other via a shared store by adding constraints to the store and checking constraints against the store. A central idea is to maintain a close connection between the logical and operational semantics of programs by using logical entailment for synchronization purposes. This project is concerned with the development of program analysis, optimization, and implementation techniques for such languages. Many of the ideas and optimization techniques extend readily to other high level declarative programming languages and dynamically typed languages.