Simon Wimmer: Verified Model Checking of Timed Automata

We have constructed a mechanically verified prototype implementation of a model checker for timed automata, a popular formalism for modeling real-time systems. Our goal is two-fold: first, we want to provide a reference implementation that is fast enough to check other model checkers against it on reasonably sized benchmarks; second, we strive for maximal feature compatibility with the state-of-the-art tool Uppaal. The starting point of our work is an existing highly abstract formalization of reachability checking of timed automata. We reduce checking of Uppaal-style models to the problem of model checking a single automaton in this abstract formalization, while retaining the ability to perform on the fly model-checking. Using the Isabelle Refinement Framework, the abstract specification of the model checker is refined, via multiple intermediate steps, to an actual imperative implementation in Standard ML. The resulting tool is evaluated on a set of standard benchmarks to demonstrate its practical usability.

(Webseite des Vortragenden: http://home.in.tum.de/~wimmers)

Maximilian Haslbeck: Hoare Logics for Time Bounds

We study three different Hoare logics for reasoning about time bounds of imperative programs and formalize them in Isabelle/HOL: a classical Hoare like logic due to Nielson, a logic with potentials due to Carbonneaux et al. and a separation logic following work by Atkey, Chagueraud and Pottier. These logics are formally shown to be sound and complete. Verification condition generators are developed and are shown sound and complete too. We also consider variants of the systems where we abstract from multiplicative constants in the running time bounds, thus supporting a big-O style of reasoning. Finally we compare the expressive power of the three systems.

(Webseite des Vortragenden: http://www21.in.tum.de/~haslbema)