Variations on mobile processes

The paper investigates a concurrent computation model, chi calculus, in which communications resemble cut eliminations for classical proofs. Two bisimilarities, local bisimilarity and barbed bisimilarity, on chi processes are studied and are shown to be congruence relations. The former equivalence turns out to be strictly stronger than the latter. It is shown that chi calculus is capable of modeling sequential computation in that it captures the operational semantics of call-by-name lambda calculus. A translation from pi calculus to chi calculus is given, demonstrating that, practically speaking, pi is a sublanguage of chi. A higher-order version of chi calculus is proposed and examined. It combines the communication mechanism of chi calculus and the recursion mechanism of full lambda calculus, and therefore extends both. (C) 1999 Elsevier Science B.V. All rights reserved.