Apr 12, 2018: Arnd Hartmanns: A Hierarchy of Scheduler Classes for Stochastic Automata

April 12, 2018A Hierarchy of Scheduler Classes for Stochastic Automata
Room: ???Arnd Hartmanns
15:45-16:45

Stochastic automata are a formal compositional model for concurrent stochastic timed systems, with general distributions and nondeterministic choices. Measures of interest are defined over schedulers that resolve the nondeterminism. We investigate the power of various theoretically and practically motivated classes of schedulers, considering the classic complete-information view and a restriction to non-prophetic schedulers. We prove a hierarchy of scheduler classes w.r.t. unbounded probabilistic reachability. We find that, unlike Markovian formalisms, stochastic automata distinguish most classes even in this basic setting. Verification and strategy synthesis methods thus face a tradeoff between powerful and efficient classes. Using lightweight scheduler sampling, we explore this tradeoff and demonstrate the concept of a useful approximative verification technique for stochastic automata. This is joint work with Pedro R. D'Argenio, Marcus Gerhold and Sean Sedwards, to be presented at FoSSaCS 2018.