Document Type

Technical Report


Computer Science and Engineering

Publication Date






Technical Report Number



Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Note that this definition is general enough to encompass a system of mobile hosts moving in physical space as well as a system of migrating software agents implemented on a set of possibly non-mobile hosts. In this paper, we present Mobile UNITY, which is a notation for expressing such systems and a logic for reasoning about their temporal properties. Based on the UNITY language of Chandy and Misra, our goal is to find a minimalist model of mobile computation that will allow us to express mobile components in a modular fashion and to reason formally about the possible behaviors of a system composed from mobile components. We also show how the model can contribute to our understanding of mobility by exploring new abstractions for loosely coupled communication and coordination among components.


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