A logic semantics for a class of nondeterministic concurrent constraint logic programs

M.J. Maher (1987) proposed the ALPS class of committed-choice languages, which can be seen as a further development of concurrent logic programming languages in the direction of CLP(X). However, due to the lack of OR-nondeterminism, ALPS is a class of declarative algorithmic programming languages. In this paper, we present the FENG class of concurrent constraint logic programming languages and give its soundness and completeness results. With the novel feature of constraint based nondeterminism, FENG enriches the semantics of the ALPS and CLP(X). One of the features of FENG is that it supports constraint bared nondeterminism. For some class of programs, this improves the efficiency of program execution. FENG reveals a direction for data-parallel implementations of constraint logic programs. This has been confirmed by our experience in design and implementation of Firebird, a restriction of FENG, on the massively parallel machine DECmpp