Formal Verification of a Distributed Computer System

Abstract

Modeling distributed computer systems is known to be a challenging enterprise. Typically, distributed systems are comprised of large numbers of components whose coordination may require complex interactions. Modeling such systems more often than not leads to the nominal intractability of the resulting state space. Various formal methods have been proposed to address the modeling of coordination among distributed systems components. For the most part, however, these methods do not support formal verification mechanisms. By way of contrast, the L-automata/L-processes model supports formal verification mechanisms which in many examples can successfully circumvent state space explosion problems, and allow verification proofs to be extended to an arbitrary number of components. After reviewing L-automata/L-processes formalisms, we present here the formal specification of a fault-tolerant algorithm for a distributed computer system. We also expose the L-automata/L-processes verification of the distributed system, demonstrating how various techniques such as homomorphic reduction, induction, and linearization, can be used to overcome various problems which surface as one models large, complex systems.