The objective of this project is to study theoretical and practical issues in the evaluation of general globel predicates and functions of distributed software. As an application of the techniques of the research, the project will focus on distributed monitoring systems for fault tolerance. An example of detecting a global predicate arises in implementing the most basic command of a monitoring system: `stop the program when the predicate is true`. To stop the program it is necessary to detect the predicate q, which is not a trivial task if q requires access to the global state. There are three components to the project: theory, algorithms and implementation. There are two questions that will be investigated in terms of theory. First, the class of global predicates that are efficient to detect will be classified. This will also entail studying the limits of efficient detection of global predicates. Second, a predicate logic which is suitable for efficient detection of global predicates will be developed. After developing the logic, efficient decentralized algorithms for detecting occurrence of logic formulas will be designed. This work will be based on the use of a centralized checker process developed by the PI. Finally, the decentralized algorithm will be used to design an experimental distributed monitoring system.
