A Modest Approach to Modelling and Checking Markov Automata.

Markov automata are a compositional modelling formalism with continuous stochastic time, discrete probabilities, and nondeterministic choices. In this paper, we present extensions to the Modest language and the mcsta model checker to describe and analyse Markov automata models. Modest is an expressive high-level language with roots in process algebra that allows large models to be specified in a succinct, modular way. We explain its use for Markov automata and illustrate the advantages over alternative languages. The verification of Markov automata models requires dedicated algorithms for time-bounded probabilistic reachability and long-run average rewards. We describe several recently developed such algorithms as implemented in mcsta and evaluate them on a comprehensive set of benchmarks. Our evaluation shows that mcsta improves the performance and scalability of Markov automata model checking compared to earlier and alternative tools.