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Abstract:We present TwoTowers, a tool for analyzing functional and performance properties of concurrent systems expressed as terms in the stochastically timed reward process algebra EMPAr. TwoTowers builds on two existing tools, CWB-NC and MarCA, that have been retargeted to carry out functional and performance analysis (respectively) of EM PAr system specifications. As an example, we describe the application of TwoTowers to the Lehmann-Rabin randomized distributed algorithm for the dining philosopher problem.

Salsa is an invariant checker for specifications in SAL (the SCR Abstract Language). To establish a formula as an invariant without any user guidance, Salsa carries out an induction proof that utilizes tightly integrated decision procedures, currently a combination of BDD algorithms and a constraint solver for integer linear arithmetic, for discharging the verification conditions. The user interface of Salsa is designed to mimic the interfaces of model checkers; i.e., given a formula and a system description, Salsa either establishes the formula as an invariant of the system (but returns no proof) or provides a counterexample. In either case, the algorithm will terminate. Unlike model checkers, Salsa returns a state pair as a counterexample and not an execution sequence. Also, due to the incompleteness of induction, users must validate the counterexamples. The use of induction enables Salsa to combat the state explosion problem that plagues model checkers -it can handle specifications whose state spaces are too large for model checkers to analyze. Also, unlike general purpose theorem provers, Salsa concentrates on a single task and gains efficiency by employing a set of optimized heuristics.

This paper describes the Process Algebra Compiler (PAC), a front-end generator for process-algebragbased verification tools. Given descriptions of a process algebra's concrete and abstract syntax and semantics as structural operational rules, the PAC produces syntactic routines and functions for computing the semantics of programs in the algebra. Using this tool greatly simplifies the task of adapting verification tools to the analysis of systems described in different languages; it may therefore be used to achieve source-level compatibility between different verification tools. Although the initial verification tools targeted by the PAC are MAUTO and the Concurrency Workbench, the structure of the PAC caters for the support of other tools as well.

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