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16
Synthesising optimal timing delays for timed i/o automata
 In EMSOFT’14. ACM
, 2014
"... In many realtime embedded systems, the choice of values for the timing delays can crucially affect the safety or quantitative characteristics of their execution. We propose a parameter synthesis algorithm that finds optimal timing delays guaranteeing that the system satisfies a given quantitative ..."
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In many realtime embedded systems, the choice of values for the timing delays can crucially affect the safety or quantitative characteristics of their execution. We propose a parameter synthesis algorithm that finds optimal timing delays guaranteeing that the system satisfies a given quantitative property. As a modelling framework we consider networks of Timed Input/Output Automata (TIOA) with priorities and parametric guards. To express system properties we extend Metric Temporal Logic (MTL) with counting formulas. We implement the algorithm using constraint solving and Monte Carlo sampling, and demonstrate the feasibility of our approach on a simplified model of a pacemaker. We are able to synthesise timing delays that ensure with high probability that energy usage is minimised, while maintaining the basic safety property of the pacemaker.
Synthesis of bounded integer parameters for parametric timed reachability games
 In ATVA, volume 8172 of Lecture Notes in Computer Science
, 2013
"... Abstract. We deal with a parametric version of timed game automata (PGA), where clocks can be compared to parameters, and parameter synthesis. As usual, parametrization leads to undecidability of the most interesting problems, such as reachability game. It is not surprising then that the symbolic ex ..."
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Abstract. We deal with a parametric version of timed game automata (PGA), where clocks can be compared to parameters, and parameter synthesis. As usual, parametrization leads to undecidability of the most interesting problems, such as reachability game. It is not surprising then that the symbolic exploration of the statespace often does not terminate. It is known that the undecidability remains even when severely restricting the form of the parametric constraints. Since in classical timed automata, realvalued clocks are always compared to integers for all practical purposes, we solve undecidability and termination issues by computing parameters as bounded integers. We give a symbolic algorithm that computes the set of winning states for a given PGA and the corresponding set of bounded integer parameter valuations as symbolic constraints between parameters. We argue the relevance of this approach and demonstrate its practical usability with a small casestudy. 1
Language Preservation Problems in Parametric Timed Automata?
, 2015
"... Abstract. Parametric timed automata (PTA) are a powerful formalism to model and reason about concurrent systems with some unknown timing delays. In this paper, we address the (untimed) language and tracepreservation problems: given a reference parameter valuation, does there exist another paramet ..."
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Abstract. Parametric timed automata (PTA) are a powerful formalism to model and reason about concurrent systems with some unknown timing delays. In this paper, we address the (untimed) language and tracepreservation problems: given a reference parameter valuation, does there exist another parameter valuation with the same untimed language (or trace)? We show that these problems are undecidable both for general PTA, and even for the restricted class of L/UPTA. On the other hand, we exhibit decidable subclasses: 1clock PTA, and 1parameter deterministic LPTA and UPTA. 1
Parameter synthesis for probabilistic timed automata using stochastic game abstractions.
, 2014
"... Abstract. We propose a 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 gua ..."
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Abstract. We propose a 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) reachability probability. To ensure precise reachability probabilities, we adapt the gamebased abstraction refinement method. In the parametric setting, our method is able to determine all the possible maximum (or minimum) reachability probabilities that arise for different values of timing parameters, and yields optimal valuations represented as a set of symbolic constraints between parameters.
Parametric Interrupt Timed Automata ⋆
"... Abstract. Parametric reasoning is particularly relevant for timed models, but very often leads to undecidability of reachability problems. We propose a parametrised version of Interrupt Timed Automata (an expressive model incomparable to Timed Automata), where polynomials of parameters can occur in ..."
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Abstract. Parametric reasoning is particularly relevant for timed models, but very often leads to undecidability of reachability problems. We propose a parametrised version of Interrupt Timed Automata (an expressive model incomparable to Timed Automata), where polynomials of parameters can occur in guards and updates. We prove that different reachability problems, including robust reachability, are decidable for this model, and we give complexity upper bounds for a fixed or variable number of clocks and parameters. 1
Parameter Synthesis for Timed Kripke Structures Extended Abstract
"... Abstract. We show how to synthesise parameter values under which a given property, expressed in a certain extension of CTL called RTCTLP, holds in a parametric timed Kripke structure. Similarly as in fixedpoint symbolic model checking approach, we introduce special operators which stabilise on the ..."
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Abstract. We show how to synthesise parameter values under which a given property, expressed in a certain extension of CTL called RTCTLP, holds in a parametric timed Kripke structure. Similarly as in fixedpoint symbolic model checking approach, we introduce special operators which stabilise on the solution. The process of stabilisation is essentially a translation from RTCTLP parameter synthesis problem to a discrete optimization task. We argue that this leads to new opportunities in model checking, including the use of integer programming and related tools. 1
Verification of Two RealTime Systems Using Parametric Timed Automata
"... Abstract—In this paper we propose solutions to the FMTV challenge of a distributed video processing system using the formalism of Parametric Timed Automata (PTA). The first challenge is harder because of the very large number of states to be analysed, so we only provide upper bounds. The second chal ..."
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Abstract—In this paper we propose solutions to the FMTV challenge of a distributed video processing system using the formalism of Parametric Timed Automata (PTA). The first challenge is harder because of the very large number of states to be analysed, so we only provide upper bounds. The second challenge consists of a realtime scheduling problem for which we provide exact solutions by using a scheduling analysis based on the critical instant, and a PTA model. I.
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"... Synthesising robust and optimal parameters for cardiac pacemakers using symbolic and evolutionary computation techniques ..."
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Synthesising robust and optimal parameters for cardiac pacemakers using symbolic and evolutionary computation techniques
Enhanced Distributed Behavioral Cartography of Parametric Timed Automata?
"... Abstract. Parametric timed automata (PTA) allow the specification and verification of timed systems incompletely specified, or subject to future changes. The behavioral cartography splits the parameter space of PTA in tiles in which the discrete behavior is uniform. Applications include the optimiza ..."
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Abstract. Parametric timed automata (PTA) allow the specification and verification of timed systems incompletely specified, or subject to future changes. The behavioral cartography splits the parameter space of PTA in tiles in which the discrete behavior is uniform. Applications include the optimization of timing constants, and the measure of the system robustness w.r.t. the untimed language. Here, we present enhanced distributed algorithms to compute the cartography efficiently. Experimental results show that our new algorithms significantly outperform previous distribution techniques.
IOS Press Parameter Synthesis for Timed Kripke Structures∗
"... Abstract. We show how to synthesise parameter values under which a given property, expressed in a certain extension of CTL, called RTCTLP, holds in a parametric timed Kripke structure. We prove the decidability of parameter synthesis for RTCTLP by showing how to restrict the infinite space of parame ..."
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Abstract. We show how to synthesise parameter values under which a given property, expressed in a certain extension of CTL, called RTCTLP, holds in a parametric timed Kripke structure. We prove the decidability of parameter synthesis for RTCTLP by showing how to restrict the infinite space of parameter valuations to its finite subset and employ a bruteforce algorithm. The bruteforce approach soon becomes intractable, therefore we propose a symbolic algorithm for RTCTLP parameter synthesis. Similarly to the fixedpoint symbolic model checking approach, we introduce special operators which stabilise on the solution. The process of stabilisation is essentially a translation from the RTCTLP parameter synthesis problem to a discrete optimization task. We show that the proposed method is sound and complete and provide some complexity results. We argue that this approach leads to new opportunities in model checking, including the use of integer programming and related tools. 1.