Better abstractions for timed automata

Lazy Abstractions for Timed Automata

We consider the reachability problem for timed automata. A standard solution to this problem involves computing a search tree whose nodes are abstractions of zones. For efficiency reasons, they are parametrized by the maximal lower and upper bounds (LU -bounds) occurring in the guards of the automaton. We propose an algorithm that is updating LU -bounds during exploration of the search tree. In...

Parameter Synthesis for Probabilistic Timed Automata Using Stochastic Game Abstractions

We propose a symbolic method to synthesise optimal values of timing parameters for probabilistic timed automata, in the sense that the probability of reaching some set of states is either maximised or minimised. Our first algorithm, based on forward exploration of the symbolic states, can only guarantee parameter values that correspond to upper (resp. lower) bounds on maximum (resp. minimum) re...

Diamonds Are a Girl's Best Friend: Partial Order Reduction for Timed Automata with Abstractions

A major obstacle for using partial order reduction in the context of real time verification is that the presence of clocks and clock constraints breaks the usual diamond structure of otherwise independent transitions. This is especially true when information of the relative values of clocks is preserved in the form of diagonal constraints. However, when diagonal constraints are relaxed by a sui...

Multi-timed Bisimulation for Distributed Timed Automata

Timed Unfoldings for Networks of Timed Automata

Whereas partial order methods have proved their efficiency for the analysis of discrete-event systems, their application to timed systems remains a challenging research topic. Here, we design a verification algorithm for networks of timed automata with invariants. Based on the unfolding technique, our method produces a branching process as an acyclic Petri net extended with read arcs. These arc...