The quest for average response time

Abstract

Responsiveness -the requirement that every request to a system be eventually handled- is one of the fundamental liveness properties of a reactive system and lies at the heart of all methods for specifying and verifying liveness. Average response time is a quantitative measure for the responsiveness requirement used commonly in performance evaluation. The static computation of average response time has proved remarkably elusive even for finite-state models of reactive systems. We present, for the first time, a robust formalism that allows the specification and computation of quantitative temporal properties including average response time. The formalism is based on nested weighted automata, which can serve as monitors for measuring the response time of a reactive system. We show thatquantitative properties specified by nested weighted automatacan be computed in exponential space for nondeterministic finite-state models of reactive systems and in polynomial time for probabilistic finite-state models.The specific property of average response time can be computed in polynomial time in both cases.This work is joint with Krishnendu Chatterjee and Jan Otop.