Abstract
In the classical shared-variable models, component processes reside on their processors and communicate by shared variables in memory shared by the processors. In this paper, we argue that shared memory is not necessary to share variables. Processes can share variables in local memories of processors if they travel among the processors. We present a formal distributed memory model in which a system can be decomposed into processes residing on processors and communicating by message passing or into processes travelling among processors and communicating by shared variables. We call this property communication dualism of distributed systems. We point out that the shared-memory monitor can be used in distributed memory and suggest that variable sharing is a convenient alternative to message passing. We also point out that a mobile agent is a kind of travelling process, but its prominent property, code mobility, is not related to shared-variable communication.