Béatrice Bérard

Characterization of the expressive power of silent transitions in timed automata

Timed automata are among the most widely studied models for real-time systems. Silent transitions, i.e., e-transitions, have already been proposed in the original paper on timed automata by Alur and Dill [3]. We show that the class TL e of timed languages recognized by automata with e-transitions, is more robust and more expressive than the corresponding class TL without e-transitions. We then focus on e-transitions without reset, i.e. e-transitions which do not reset clocks. We propose an algorithm to construct, given a timed automaton, an equivalent one without such transitions. This algorithm is in two steps, it first suppresses the cycles of e-transitions without reset and then the remaining ones. Then, we prove that a timed automaton such that no e-transition which resets clocks lies on any directed cycle, can be effectively transformed into a timed automaton without etransitions. Interestingly, this main result holds under the assumption of non-Zenoness and it is false otherwise. To complete the picture, we exhibit a simple timed automaton with an e-transition, which resets some clock, on a cycle and which is not equivalent to any e-free timed automaton. To show this, we develop a promising new technique based on the notion of precise action. This paper presents a synthesis of the two conference communications [9] and [13].

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

Comparison of different semantics for time petri nets

\mathcal{A}

Quantifying Opacity

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

On the Power of Non-Observable Actions in Timed Automata

\mathcal{A}

When are timed automata weakly timed bisimilar to time petri nets

. 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

Formal verification of mobile robot protocols

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

When are Timed Automata weakly timed bisimilar to Time Petri Nets

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

Accepting Zeno words: a way toward timed refinements

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

Real Time Properties for Interrupt Timed Automata

, bounded and 1-safe TPNs “a la Merlin” are equally expressive w.r.t. timed bisimilarity.