Denotational semantics of channel mobility in UTP-CSP

Abstract

In this paper, we present the denotational semantics for channelmobility in the Unifying Theories of Programming (UTP) semanticsframework. The basis for the model is the UTP theory of reactiveprocesses, precisely, the UTP semantics for Communicating SequentialProcesses (CSP), which is extended to allow the mobility ofchannels—the set of channels that a process can use forcommunication (its interface), originally static or constant (setduring the process's definition), is now made dynamic or variable:it can change during the process's execution. A channel is thusmoved around by communicating it via other channels and thenallowing the receiving process to extend its interface with thereceived channel. We introduce a new concept, the capability of a process, which allows separating the ownership of channels fromthe knowledge of their existence. Mobile processes are then definedas having a static capability and a dynamic interface. Operations ofa mobile telecommunications network, e.g., handover, load balancing,are used to illustrate the semantics. We redefine CSP operators andin particular provide the first semantics for the renaming andhiding operators in the context of channel mobility.