Document Type

Technical Report


Computer Science and Engineering

Publication Date






Technical Report Number



The current trend toward portable computing systems (e.g., cellular phones, laptop computers) brings with it the need for a new paradigm for thinking about designing distributed applications. We introduce the term mobile to refer to distributed systems that include moving, autonomous agents which loosely cooperate to accomplish a tastk. The fluid nature of hte interconnections between components in a mobile system provides new challenges and new opportunities for the research community. While we do not propsoe to have fully grasped the consequences of these systems, we believe that the notions of place, time, and action will be central in any model that is developed. In this paper, we show that these concepts can be expressed and reasoned about in the UNITY logic with a minimal amount of additional notation. We choose as an example an elevator control system, with minor modifications to give the system mobile characteristics. We begin with a high-level specification of the control system, one which does not include any mobile characteristics, and introduce the notions of place, time, and action as they arise in the specification refinement process. The result of the refinement is an abstract program, a specification of the local actions of the system along with restrictions on teh cooperation patterns between the various components.


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