Conjunctive Predicate Detection

This paper discusses efficient detection of global predicates in a distributed program. Previous work in detection of global predicates was restricted to predicates that could be specified as a boolean formula of local predicates. Many properties in distributed systems, however, use the state of channels. In this paper, we introduce the concept of a channel predicate and provide an efficient algorithm to detect any boolean formula of local and channel predicates. We define a property called monotonicity for channel predicates. Monotonicity is crucial for efficient detection of global predicates. We show that many problems studied earlier, such as detection of termination and computation of global virtual time are special cases of the problem considered in this paper. The message complexity of our algorithm is bounded by the number of messages used by the program. The main application of our results are in debugging and testing of distributed programs. Our algorithms have been incorpora..