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60
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 63 (27 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
Task Automata: Schedulability, Decidability and Undecidability
, 2008
"... We present a model, task automata, for real time systems with nonuniformly recurring computation tasks. It is an extended version of timed automata with asynchronous processes that are computation tasks generated (or triggered) by timed events. Compared with classical task models for real time syst ..."
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Cited by 58 (9 self)
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We present a model, task automata, for real time systems with nonuniformly recurring computation tasks. It is an extended version of timed automata with asynchronous processes that are computation tasks generated (or triggered) by timed events. Compared with classical task models for real time systems, task automata may be used to describe tasks (1) that are generated nondeterministically according to timing constraints in timed automata, (2) that may have interval execution times representing the best case and the worst case execution times, and (3) whose completion times may influence the releases of task instances. We generalize the classical notion of schedulability to task automata. A task automaton is schedulable if there exists a scheduling strategy such that all possible sequences of events generated by the automaton are schedulable in the sense that all associated tasks can be computed within their deadlines. Our first technical result is that the schedulability for a given scheduling strategy can be checked algorithmically for the class of task automata when the best case and the worst case execution times of tasks are equal. The proof is based on a decidable class of suspension automata: timed automata with bounded subtraction in which clocks may be updated by subtractions within a bounded zone. We shall also study the borderline between decidable and undecidable cases. Our second technical result shows that the schedulability checking problem will be undecidable if the following three conditions hold: (1) the execution times of tasks are intervals, (2) the precise finishing time of a task instance may influence new task releases, and (3) a task is allowed to preempt another running task.
Guided Synthesis of Control Programs Using UPPAAL
, 2000
"... In this paper we address the problem of scheduling and synthesizing distributed control programs for a batch production plant. We use a timed automata model of the batch plant and the verification tool UPPAAL to solve the scheduling problem. The plant model aims at faithfully reflecting the level of ..."
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Cited by 58 (27 self)
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In this paper we address the problem of scheduling and synthesizing distributed control programs for a batch production plant. We use a timed automata model of the batch plant and the verification tool UPPAAL to solve the scheduling problem. The plant model aims at faithfully reflecting the level of abstraction required for synthesizing control programs from generated timed traces. Therefore it quickly becomes too detailed and complicated for automatic synthesis. To solve this problem we present a general way of adding guidance to a model by augmenting it with additional guidance variables and decorating the transitions with extra guards. Applying this technique have made synthesis of control programs feasible for a plant producing as many as 60 batches. In comparison, we could only handle plants producing two batches without using guides. The synthesized control programs have been executed in a physical plant. This proved useful in validating the correctness of the plant model and in ...
Timed automata with asynchronous processes: schedulability and decidability
 In Proceedings of TACAS 2002
, 2002
"... Abstract. In this paper, we exend timed automata with asynchronous processes i.e. tasks triggered by events as a model for realtime systems. The model is expressive enough to describe concurrency and synchronization, and real time tasks which may be periodic, sporadic, preemptive or nonpreemptive. ..."
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Cited by 51 (11 self)
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Abstract. In this paper, we exend timed automata with asynchronous processes i.e. tasks triggered by events as a model for realtime systems. The model is expressive enough to describe concurrency and synchronization, and real time tasks which may be periodic, sporadic, preemptive or nonpreemptive. We generalize the classic notion of schedulability to timed automata. An automaton is schedulable if there exists a scheduling strategy such that all possible sequences of events accepted by the automaton are schedulable in the sense that all associated tasks can be computed within their deadlines. We believe that the model may serve as a bridge between scheduling theory and automatatheoretic approaches to system modeling and analysis. Our main result is that the schedulability checking problem is decidable. To our knowledge, this is the first general decidability result on densetime models for real time scheduling without assuming that preemptions occur only at integer time points. The proof is based on a decidable class of updatable automata: timed automata with subtraction in which clocks may be updated by subtractions within a bounded zone. The crucial observation is that the schedulability checking problem can be encoded as a reachability problem for such automata. Based on the proof, we have developed a symbolic technique and a prototype tool for schedulability analysis. 1
Efficient Guiding Towards CostOptimality in UPPAAL
, 2001
"... In this paper we present an algorithm for efficiently computing the minimum cost of reaching a goal state in the model of Uniformly Priced Timed Automata (UPTA). This model can be seen as a submodel of the recently suggested model of linearly priced timed automata, which extends timed automata with ..."
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Cited by 42 (22 self)
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In this paper we present an algorithm for efficiently computing the minimum cost of reaching a goal state in the model of Uniformly Priced Timed Automata (UPTA). This model can be seen as a submodel of the recently suggested model of linearly priced timed automata, which extends timed automata with prices on both locations and transitions. The presented algorithm is based on a symbolic semantics of UTPA, and an efficient representation and operations based on difference bound matrices. In analogy with Dijkstra's shortest path algorithm, we show that the search order of the algorithm can be chosen such that the number of symbolic states explored by the algorithm is optimal, to be optimal, in the sense that the number of explored states can not be reduced by any other search order. We also present a number of techniques inspired by branchandbound algorithms which can be used for limiting the search space and for quickly finding nearoptimal solutions. The algorithm has been implemented in the verification tool Uppaal. When applied on a number of experiments the presented techniques reduced the explored statespace with up to 90%.
JobShop Scheduling using Timed Automata
"... In this paper we show how the classical jobshop scheduling problem can be modeled as a special class of acyclic timed automata. Finding an optimal schedule corresponds, then, to nding a shortest (in terms of elapsed time) path in the timed automaton. This representation provides new techniques for ..."
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Cited by 42 (8 self)
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In this paper we show how the classical jobshop scheduling problem can be modeled as a special class of acyclic timed automata. Finding an optimal schedule corresponds, then, to nding a shortest (in terms of elapsed time) path in the timed automaton. This representation provides new techniques for solving the optimization problem and, more importantly, it allows to model naturally more complex dynamic resource allocation problems which are not captured so easily in traditional models of operation research. We present several algorithms and heuristics for nding the shortest paths in timed automata and test their implementation in the tool Kronos on numerous benchmark examples.
As Cheap as Possible: Efficient CostOptimal Reachability for Priced Timed Automata
, 2001
"... In this paper we present an algorithm for efficiently computing optimal cost of reaching a goal state in the model of Linearly Priced Timed Automata (LPTA). In recent papers, this problem have been shown to be computable using a priced extention of the traditional notion of regions for timed automat ..."
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Cited by 40 (11 self)
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In this paper we present an algorithm for efficiently computing optimal cost of reaching a goal state in the model of Linearly Priced Timed Automata (LPTA). In recent papers, this problem have been shown to be computable using a priced extention of the traditional notion of regions for timed automata. However, for efficiency it is imperative that the computation is based on socalled zones (i.e. convex set of clock valuations) rather than regions. The central contribution of this paper is a priced extension of zones. This, together with a notion of facets of a zone, allows the entire machinery for symbolic reachability in terms of zones to be lifted to costoptimal reachability using priced zones. We report on experiments with a costoptimizing extension of Uppaal on a number of examples, including a range of aircraft landing problems.
Static Analysis and Dynamic Steering of TimeDependent Systems
 IEEE Transactions on Software Engineering
, 1998
"... An enumerative technique is presented which supports reachability and timeliness analysis of timedependent models based. The technique assumes a dense model of time and uses equivalence classes to enable discrete and compact enumeration of the state space. Properties of timed reachability among sta ..."
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Cited by 39 (24 self)
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An enumerative technique is presented which supports reachability and timeliness analysis of timedependent models based. The technique assumes a dense model of time and uses equivalence classes to enable discrete and compact enumeration of the state space. Properties of timed reachability among states are recovered through the analysis of timing constraints embedded within equivalence classes. In particular, algorithms are given to evaluate a tight profile for the set of feasible timings of any untimed run. Run time refinement of static profiles supports a mixed static/dynamic strategy in the development of a failure avoidance mechanism for dynamic acceptance and guarantee of hard real time processes.
Staying Alive As Cheaply As Possible
 IN PROC. OF 7TH INTL. WORKSHOP ON HYBRID SYSTEMS: COMPUTATION AND CONTROL (HSCC), VOLUME 2993 OF LECT. NOTES IN COMP. SCI
, 2004
"... This paper is concerned with the derivation of infinite schedules for timed automata that are in some sense optimal. To cover a wide class of optimality criteria we start out by introducing an extension of the (priced) timed automata model that includes both costs and rewards as separate modellin ..."
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Cited by 39 (21 self)
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This paper is concerned with the derivation of infinite schedules for timed automata that are in some sense optimal. To cover a wide class of optimality criteria we start out by introducing an extension of the (priced) timed automata model that includes both costs and rewards as separate modelling features. A precise definition is then given of what constitutes optimal infinite behaviours for this class of models. We subsequently show that the derivation of optimal nonterminating schedules for such doublepriced timed automata is computable. This