A Lightweight Coordination Model and Middleware for Mobile Computing

Limone is a new coordination model and middleware that enables rapid application development for wireless ad hoc networks entailing logical mobility of agents and physical mobility of hosts. Designed to function in open environments, Limone performs automatic agent discovery but filters the results to define for each agent an individualized acquaintance list in accordance with run-time policies that are customizable by the application. This asymmetry among participants represents a new direction in coordination research and is dictated by the need to accommodate settings involving large numbers of agents and hosts that come and go freely. The coordination context is limited to the specific needs of the individual agent and its coordination activities are restricted to tuple spaces owned by peers present in the acquaintance list. Designed for wireless ad hoc networks, Limone tailors Linda-like primitives to address the challenges of mobile environments. This entails the elimination of remote blocking operations and the addition of timeouts to all distributed operations since disconnection with the affected agents may occur at any time. It also entails the addition of reactions that are triggered by the presence of information of interest on agents listed in the acquaintance list. Finally, to ensure performance and ease of deployment on small devices the granularity of atomic operations and the assumptions about the environment have been minimized. This paper introduces Limone, explains its key features, illustrates its usage, and explores its effectiveness as a software engineering tool.