Indeterminate Concurrent Constraint Programming :

This paper presents a semantics for non-deterministic concurrent constraint programming languages. The semantics address the issues of giving an adequate treatment of non-terminating computations, in particular with fairness and liveness, and giving a compositional semantics, where the meaning of a recursively deened program is obtained as a xpoint. We present a simple concurrent constraint programming language with a reduction rule semantics , which is augmented with fairness requirements. We specify how traces are obtained from fair computations of a program. The operational semantics of a program is deened as the set of traces of the program. We show that this trace semantics can be deened compositionally. The trace semantics is transformed into a continuous xpoint semantics, using the framework of Lehmann's category-theoretic constructions, and present a general schema for deening continuous operators on the semantic domain. A simple abstraction operator is deened, and is proved to give a fully abstract semantics. This article was published in the proceedings of the 1993 international symposium on logic programming.