A distributed calculus with local areas of communication

This paper introduces a process calculus designed to capture the phenomenon of names which are known universally but always refer to local information. Our system extends the π-calculus so that a channel name can have within its scope several disjoint local areas. Such a channel name may be used for communication within an area, it may be sent between areas, but it cannot itself be used to transmit information from one area to another. Areas are arranged in a hierarchy of levels, distinguishing for example between a single application, a machine, or a whole network. We give an operational semantics for the calculus, and develop a type system that guarantees the proper use of channels within their local areas. We illustrate with models of an internet service protocol and a pair of distributed agents.