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35
Optimal strategies in priced timed game automata
 In FSTTCS 04, LNCS 3328
, 2004
"... Abstract. Priced timed (game) automata extend timed (game) automata with costs on both locations and transitions. In this paper we focus on reachability games for priced timed game automata and prove that the optimal cost for winning such a game is computable under conditions concerning the nonzeno ..."
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Cited by 49 (23 self)
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Abstract. Priced timed (game) automata extend timed (game) automata with costs on both locations and transitions. In this paper we focus on reachability games for priced timed game automata and prove that the optimal cost for winning such a game is computable under conditions concerning the nonzenoness of cost and we prove that it is decidable. Under stronger conditions (strictness of constraints) we prove that in case an optimal strategy exists, we can compute a statebased winning optimal strategy. 1
Shrinking timed automata
 In FSTTCS’11, LIPIcs 13, p. 375–386. LeibnizZentrum für Informatik
, 2011
"... We define and study a new approach to the implementability of timed automata, where the semantics is perturbed by imprecisions and finite frequency of the hardware. In order to circumvent these effects, we introduce parametric shrinking of clock constraints, which corresponds to tightening these. We ..."
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Cited by 30 (10 self)
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We define and study a new approach to the implementability of timed automata, where the semantics is perturbed by imprecisions and finite frequency of the hardware. In order to circumvent these effects, we introduce parametric shrinking of clock constraints, which corresponds to tightening these. We propose symbolic procedures to decide the existence of (and then compute) parameters under which the shrunk version of a given timed automaton is nonblocking and can timeabstract simulate the exact semantics. We then define an implementation semantics for timed automata with a digital clock and positive reaction times, and show that for shrinkable timed automata, nonblockingness and timeabstract simulation are preserved in implementation.
Implementation of timed automata: an issue of semantics or modeling
 In Proc. 3rd Int. Conf. Formal Modelling and Analysis of Timed Systems (FORMATS’05), Lecture Notes in Computer Science
, 2005
"... Abstract. We examine to what extent implementation of timed automata can be achieved using the standard semantics and appropriate modeling, instead of introducing new semantics. We propose an implementation methodology which allows to transform a timed automaton into a program and to check whether t ..."
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Cited by 24 (3 self)
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Abstract. We examine to what extent implementation of timed automata can be achieved using the standard semantics and appropriate modeling, instead of introducing new semantics. We propose an implementation methodology which allows to transform a timed automaton into a program and to check whether the execution of this program on a given platform satisfies a desired property. This is done by modeling the program and the execution platform, respectively, as an untimed automaton and a collection of timed automata. We also study the problem of property preservation, in particular when moving to a “better” execution platform. We show that some subtleties arise regarding the definition of “better”, in particular for digital clocks. The fundamental issue is that faster clocks result in better “sampling ” and therefore can introduce more behaviors. 1
Robustness and Implementability of Timed Automata
 In Proc. Joint Conf. Formal Modelling and Analysis of Timed Systems and Formal Techniques in RealTime and Fault Tolerant System (FORMATS+FTRTFT’04), volume 3253 of LNCS
, 2004
"... In a former paper, we de ned a new semantics for timed automata, the Almost ASAP semantics, which is parameterized by to cope with the reaction delay of the controller. We showed that this semantics is implementable provided there exists a strictly positive value for the parameter for which t ..."
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Cited by 19 (9 self)
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In a former paper, we de ned a new semantics for timed automata, the Almost ASAP semantics, which is parameterized by to cope with the reaction delay of the controller. We showed that this semantics is implementable provided there exists a strictly positive value for the parameter for which the strategy is correct. In this paper, we de ne the implementability problem to be the question of existence of such a . We show that this question is closely related to a notion of robustness for timed automata de ned in [Pur98] and prove that the implementability problem is decidable.
Robust modelchecking of lineartime properties in timed automata
 PROCEEDINGS OF THE 7TH LATIN AMERICAN SYMPOSIUM ON THEORETICAL INFORMATICS (LATIN’06), VOLUME 3887 OF LECTURE
"... Formal verification of timed systems is well understood, but their implementation is still challenging. Raskin et al. have recently brought out a model of parameterized timed automata in which the transitions might be slightly delayed or expedited. This model is used to prove that a timed system is ..."
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Cited by 10 (5 self)
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Formal verification of timed systems is well understood, but their implementation is still challenging. Raskin et al. have recently brought out a model of parameterized timed automata in which the transitions might be slightly delayed or expedited. This model is used to prove that a timed system is implementable with respect to a safety property, by proving that the parameterized model robustly satisfies the safety property. We extend here the notion of implementability to the broader class of lineartime properties, and provide PSPACE algorithms for the robust modelchecking of Büchilike and LTL properties. We also show how those algorithms can be adapted in order to verify boundedresponsetime properties.
Robust analysis of timed automata via channel machines
, 2007
"... Whereas formal verification of timed systems has become a very active field of research, the idealised mathematical semantics of timed automata cannot be faithfully implemented. Several works have thus focused on a modified semantics of timed automata which ensures implementability, and robust mod ..."
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Cited by 10 (5 self)
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Whereas formal verification of timed systems has become a very active field of research, the idealised mathematical semantics of timed automata cannot be faithfully implemented. Several works have thus focused on a modified semantics of timed automata which ensures implementability, and robust modelchecking algorithms for safety, and later LTL properties have been designed. Recently, a new approach has been proposed, which reduces (standard) modelchecking of timed automata to other verification problems on channel machines. Thanks to a new encoding of the modified semantics as a network of timed systems, we propose an original combination of both approaches, and prove that robust modelchecking for coFlatMTL, a large fragment of MTL, is EXPSPACEComplete.
Probabilistic and Topological Semantics for Timed Automata
"... Like most models used in modelchecking, timed automata are an idealized mathematical model used for representing systems with strong timing requirements. In such mathematical models, properties can be violated, due to unlikely (sequences of) events. We propose two new semantics for the satisfactio ..."
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Cited by 8 (1 self)
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Like most models used in modelchecking, timed automata are an idealized mathematical model used for representing systems with strong timing requirements. In such mathematical models, properties can be violated, due to unlikely (sequences of) events. We propose two new semantics for the satisfaction of LTL formulas, one based on probabilities, and the other one based on topology, to rule out these sequences. We prove that the two semantics are equivalent and lead to a PSPACEComplete modelchecking problem for LTL over finite executions.
Robustness in realtime systems
 In SIES’11
"... We review several aspects of robustness of realtime systems, and present recent results on the robust verification of timed automata. 1 ..."
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Cited by 6 (3 self)
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We review several aspects of robustness of realtime systems, and present recent results on the robust verification of timed automata. 1
Robust reachability in timed automata: A gamebased approach
 Lab. Specification & Verification, ENS
, 2012
"... Abstract. Reachability checking is one of the most basic problems in verification. By solving this problem, one synthesizes a strategy that dictates the actions to be performed for ensuring that the target location is reached. In this work, we are interested in synthesizing “robust ” strategies for ..."
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Cited by 6 (3 self)
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Abstract. Reachability checking is one of the most basic problems in verification. By solving this problem, one synthesizes a strategy that dictates the actions to be performed for ensuring that the target location is reached. In this work, we are interested in synthesizing “robust ” strategies for ensuring reachability of a location in a timed automaton; with “robust”, we mean that it must still ensure reachability even when the delays are perturbed by the environment. We model this perturbed semantics as a game between the controller and its environment, and solve the parameterized robust reachability problem: we show that the existence of an upper bound on the perturbations under which there is a strategy reaching a target location is EXPTIMEcomplete. 1
Sampled Semantics of Timed Automata
"... Sampled semantics of timed automata is a finite approximation of their dense time behavior. While the former is closer to the actual character of the latter makes it appealing for system modeling and verification. We study one aspect of the relation between these two semantics, namely checking wheth ..."
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Cited by 6 (0 self)
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Sampled semantics of timed automata is a finite approximation of their dense time behavior. While the former is closer to the actual character of the latter makes it appealing for system modeling and verification. We study one aspect of the relation between these two semantics, namely checking whether the system exhibits some qualitative (untimed) behaviors in the dense time which cannot be reproduced by any implementation with a fixed sampling rate. More formally, the sampling problem is to decide whether there is a sampling rate such that all qualitative behaviors (the untimed language) accepted by a given timed automaton in dense time semantics can be also accepted in sampled semantics. We show that this problem is decidable.