Franck Cassez

The Impressive Power of Stopwatches

In this paper we define and study the class of stopwatch automata which are timed automata augmented with stopwatches and unobservable behaviour. In particular, we investigate the expressive power of this class of automata, and show as a main result that any finite or infinite timed language accepted by a linear hybrid automaton is also acceptable by a stopwatch automaton. The consequences of this result are two-fold: firstly, it shows that the seemingly minor upgrade from timed automata to stopwatch automata immediately yields the full expressive power of linear hybrid automata. Secondly, reachability analysis of linear hybrid automata may effectively be reduced to reachability analysis of stopwatch automata. This, in turn, may be carried out using an easy (over-approximating) extension of the efficient reachability analysis for timed automata to stopwatch automata. We report on preliminary experiments on analyzing translations of linear hybrid automata using a stopwatch-extension of the real-time verification tool UPPAAL.

Structural translation from time petri nets to timed automata

Abstract In this paper, we consider Time Petri Nets (TPN) where time is associated with transitions. We give a formal semantics for TPNs in terms of Timed Transition Systems. Then, we propose a translation from TPNs to Timed Automata (TA) that preserves the behavioral semantics (timed bisimilarity) of the TPNs. For the theory of TPNs this result is twofold: (i) reachability problems and more generally TCTL model-checking are decidable for bounded TPNs; (ii) allowing strict time constraints on transitions for TPNs preserves the results described in (i). The practical applications of the translation are: (i) one can specify a system using both TPNs and Timed Automata and a precise semantics is given to the composition; (ii) one can use existing tools for analyzing timed automata (like K ronos , U ppaal or C mc ) to analyze TPNs. In this paper we describe the new feature of the tool R omeo that implements our translation of TPNs in the U ppaal input format. We also report on experiments carried out on various examples and compare the result of our method to state-of-the-art tool for analyzing TPNs.

A Comparison of Control Problems for Timed and Hybrid Systems

In the literature, we find several formulations of the control problem for timed and hybrid systems. We argue that formulations where a controller can cause an action at any point in dense (rational or real) time are problematic, by presenting an example where the controller must act faster and faster, yet causes no Zeno effects (say, the control actions are at times 0, 1/2, 1, 1 1/4, 2, 2 1/8, 3, 3 1/16, . . . ). Such a controller is, of course, not implementable in software. Such controllers are avoided by formulations where the controller can cause actions only at discrete (integer) points in time. While the resulting control problem is well-understood if the time unit, or sampling rate of the controller, is fixed a priori, we define a novel, stronger formulation: the discrete-time control problem with unknown sampling rate asks if a sampling controller exists for some sampling rate. We prove that this problem is undecidable even in the special case of timed automata.

Comparison of the expressiveness of timed automata and time petri nets

In this paper we consider the model of Time Petri Nets (TPN) where time is associated with transitions. We also consider Timed Automata (TA) as defined by Alur & Dill, and compare the expressiveness of the two models w.r.t. timed language acceptance and (weak) timed bisimilarity. We first prove that there exists a TA

Structural Translation from Time Petri Nets to Timed Automata

mathcal{A}

The expressive power of time Petri nets

s.t. there is no TPN (even unbounded) that is (weakly) timed bisimilar to

Compilation of the ELECTRE reactive language into finite transition systems

mathcal{A}

From Time Petri Nets to Timed Automata

. We then propose a structural translation from TA to (1-safe) TPNs preserving timed language acceptance. Further on, we prove that the previous (slightly extended) translation also preserves weak timed bisimilarity for a syntactical subclass

Skink: Static Analysis of Programs in LLVM Intermediate Representation

mathcal{T}_{syn}(leq,geq)

Efficient and Scalable Runtime Monitoring for Cyber–Physical System

of TA. For the theory of TPNs, the consequences are: 1) TA, bounded TPNs and 1-safe TPNs are equally expressive w.r.t. timed language acceptance; 2) TA are strictly more expressive than bounded TPNs w.r.t. timed bisimilarity; 3) The subclass