This paper presents a formal system based on the notion of objects and asynchronous communication. Built on Milner's work on ß-calculus, the communication primitive of the formal system is purely asynchronous, which makes it unique among various concurrency formalisms. Computationally this results in a consistent reduction of Milner's calculus, while retaining the same expressive power. Seen semantically asynchronous communication induces a surprisingly different framework where bisimulation is strictly more general than its synchronous counterpart. This paper shows basic construction of the formal system along with several illustrative examples. 1 Introduction The formal system introduced in this paper is intended to accomplish two purposes. First, it provides a simple and rigorous formalism which encapsulates essential features of concurrent object-orientation [26, 25]. Being successful as a programming methodology for dynamic concurrent computing, its theoretical contents are far f...

This paper presents some results concerning equational theories for an elementary calculus based on a fragment of Milner's ß-calculus. The system is interesting because it realises asynchronous message passing not by extending but reducing the original fragment, while preserving the computational power. The bisimulation based on a novel asynchronous transition system is introduced and studied. Presented results include congruence of the bisimilarity for the calculus, its relationship with two other asynchronous theories based on traces and failures, strict inclusion of its synchronous counterpart in the asynchronous theory, and the method called the I completion that transforms two asynchronously bisimilar terms into synchronously bisimilar ones. 1 Introduction This paper presents some results concerning equational theories for an elementary calculus based on a fragment of Milner's ß-calculus [22]. The calculus, which first appeared in its present form in [12], expresses asynchronous...