Formal development of cooperative exception handling for mobile agent systems

Abstract

Mobile agent systems often require sophisticated cooperation and coordination during error detection and recovery. In this paper we propose novel fault tolerance mechanisms that support co-operative exception handling in such systems. The paper demonstrates how mechanisms like these can be formally developed and analysed. We start with identifying the typical modes of failures in agents and analysing possible failure and recovery scenarios in mobile systems. Stepwise refinement is used as our formal framework for top-down development and verification. Using the framework we formally verify the essential model properties, such as interoperability, local and global state consistency and termination of error recovery. Our approach provides developers with formal generic patterns for incorporating fault- tolerance mechanisms into mobile agent systems. We also demonstrate how the results of our formal development can be instantiated and reused in developing real-world agent software.in a search for resources or other agents. Openness allows a number of agents from different administration domains to form multi-agent applications. Anonymity is collateral to openness and equally essential for decoupling, security and scalability. Agents are autonomous because they participate in a multi-agent application to achieve their own goals, so they do not have to follow protocols enforced by the third parties.