Simulation-verification: biting at the state explosion problem

Simulation and verification are the two conventional techniques for the analysis of specifications of real-time systems. While simulation is relatively inexpensive in terms of execution time, it only validates the behavior of a system for one particular computation path. On the other hand, verification provides guarantees over the entire set of computation paths of a system, but is, in general, very expensive due to the state-space explosion problem. In this paper, we introduce a new technique: Simulation-verification combines the best of both worlds by synthesizing an intermediate analysis method. This method uses simulation to limit the generation of a computation graph to that set of computations consistent with the simulation. This limited computation graph, called a simulationverification graph, can be one or more orders of magnitude smaller than the full computation graph. A tool, XSVT, is described which implements simulation-verification graphs. Three paradigms for using the new technique are proposed. The paper illustrates the application of the proposed technique via an example of a robot controller for a manufacturing assembly line.