Results 1  10
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13
Better quality in synthesis through quantitative objectives
 In CoRR, abs/0904.2638
, 2009
"... Abstract. Most specification languages express only qualitative constraints. However, among two implementations that satisfy a given specification, one may be preferred to another. For example, if a specification asks that every request is followed by a response, one may prefer an implementation tha ..."
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Cited by 57 (18 self)
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Abstract. Most specification languages express only qualitative constraints. However, among two implementations that satisfy a given specification, one may be preferred to another. For example, if a specification asks that every request is followed by a response, one may prefer an implementation that generates responses quickly but does not generate unnecessary responses. We use quantitative properties to measure the “goodness ” of an implementation. Using games with corresponding quantitative objectives, we can synthesize “optimal ” implementations, which are preferred among the set of possible implementations that satisfy a given specification. In particular, we show how automata with lexicographic meanpayoff conditions can be used to express many interesting quantitative properties for reactive systems. In this framework, the synthesis of optimal implementations requires the solution of lexicographic meanpayoff games (for safety requirements), and the solution of games with both lexicographic meanpayoff and parity objectives (for liveness requirements). We present algorithms for solving both kinds of novel graph games. 1
Assumeguarantee verification for probabilistic systems
, 2009
"... Abstract. We present a compositional verification technique for systems that exhibit both probabilistic and nondeterministic behaviour. We adopt an assumeguarantee approach to verification, where both the assumptions made about system components and the guarantees that they provide are regular sa ..."
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Cited by 43 (15 self)
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Abstract. We present a compositional verification technique for systems that exhibit both probabilistic and nondeterministic behaviour. We adopt an assumeguarantee approach to verification, where both the assumptions made about system components and the guarantees that they provide are regular safety properties, represented by finite automata. Unlike previous proposals for assumeguarantee reasoning about probabilistic systems, our approach does not require that components interact in a fully synchronous fashion. In addition, the compositional verification method is efficient and fully automated, based on a reduction to the problem of multiobjective probabilistic model checking. We present asymmetric and circular assumeguarantee rules, and show how they can be adapted to form quantitative queries, yielding lower and upper bounds on the actual probabilities that a property is satisfied. Our techniques have been implemented and applied to several large case studies, including instances where conventional probabilistic verification is infeasible. 1
H.: Quantitative multiobjective verification for probabilistic systems
, 2010
"... Abstract. We present a verification framework for analysing multiple quantitative objectives of systems that exhibit both nondeterministic and stochastic behaviour. These systems are modelled as probabilistic automata, enriched with cost or reward structures that capture, for example, energy usage ..."
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Cited by 24 (18 self)
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Abstract. We present a verification framework for analysing multiple quantitative objectives of systems that exhibit both nondeterministic and stochastic behaviour. These systems are modelled as probabilistic automata, enriched with cost or reward structures that capture, for example, energy usage or performance metrics. Quantitative properties of these models are expressed in a specification language that incorporates probabilistic safety and liveness properties, expected total cost or reward, and supports multiple objectives of these types. We propose and implement an efficient verification framework for such properties and then present two distinct applications of it: firstly, controller synthesis subject to multiple quantitative objectives; and, secondly, quantitative compositional verification. The practical applicability of both approaches is illustrated with experimental results from several large case studies. 1
Measuring and synthesizing systems in probabilistic environments
 CoRR
"... Abstract. Often one has a preference order among the different systems that satisfy a given specification. Under a probabilistic assumption about the possible inputs, such a preference order is naturally expressed by a weighted automaton, which assigns to each word a value, such that a system is pre ..."
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Cited by 22 (11 self)
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Abstract. Often one has a preference order among the different systems that satisfy a given specification. Under a probabilistic assumption about the possible inputs, such a preference order is naturally expressed by a weighted automaton, which assigns to each word a value, such that a system is preferred if it generates a higher expected value. We solve the following optimalsynthesis problem: given an omegaregular specification, a Markov chain that describes the distribution of inputs, and a weighted automaton that measures how well a system satisfies the given specification under the given input assumption, synthesize a system that optimizes the measured value. For safety specifications and measures that are defined by meanpayoff automata, the optimalsynthesis problem amounts to finding a strategy in a Markov decision process (MDP) that is optimal for a longrun average reward objective, which can be done in polynomial time. For general omegaregular specifications, the solution rests on a new, polynomialtime algorithm for computing optimal strategies in MDPs with meanpayoff parity objectives. We present some experimental results showing optimal systems that were automatically generated in this way. 1
Energy and meanpayoff games with imperfect information
 In CSL 2010, volume LNCS 6247
, 2010
"... Abstract. We consider twoplayer games with imperfect information and quantitative objective. The game is played on a weighted graph with a state space partitioned into classes of indistinguishable states, giving players partial knowledge of the state. In an energy game, the weights represent resour ..."
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Cited by 18 (2 self)
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Abstract. We consider twoplayer games with imperfect information and quantitative objective. The game is played on a weighted graph with a state space partitioned into classes of indistinguishable states, giving players partial knowledge of the state. In an energy game, the weights represent resource consumption and the objective of the game is to maintain the sum of weights always nonnegative. In a meanpayoff game, the objective is to optimize the limitaverage usage of the resource. We show that the problem of determining if an energy game with imperfect information with fixed initial credit has a winning strategy is decidable, while the question of the existence of some initial credit such that the game has a winning strategy is undecidable. This undecidability result carries over to meanpayoff games with imperfect information. On the positive side, using a simple restriction on the game graph (namely, that the weights are visible), we show that these problems become EXPTIMEcomplete. 1
Two challenges in embedded systems design: predictability and robustness.
 The Institution of Engineering and Technology),
, 2008
"... Abstract. We discuss two main challenges in embedded systems design: the challenge to build predictable systems, and the challenge to build robust systems. We suggest how predictability can be formalized as a form of determinism, and robustness, as a form of continuity. ..."
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Cited by 10 (4 self)
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Abstract. We discuss two main challenges in embedded systems design: the challenge to build predictable systems, and the challenge to build robust systems. We suggest how predictability can be formalized as a form of determinism, and robustness, as a form of continuity.
Probabilistic Weighted Automata
"... Abstract. Nondeterministic weighted automata are finite automata with numerical weights on transitions. They define quantitative languages L that assign to each word w a real number L(w). The value of an infinite word w is computed as the maximal value of all runs over w, and the value of a run as t ..."
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Cited by 9 (2 self)
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Abstract. Nondeterministic weighted automata are finite automata with numerical weights on transitions. They define quantitative languages L that assign to each word w a real number L(w). The value of an infinite word w is computed as the maximal value of all runs over w, and the value of a run as the maximum, limsup, liminf, limit average, or discounted sum of the transition weights. We introduce probabilistic weighted automata, in which the transitions are chosen in a randomized (rather than nondeterministic) fashion. Under almostsure semantics (resp. positive semantics), the value of a word w is the largest real v such that the runs over w have value at least v with probability 1 (resp. positive probability). We study the classical questions of automata theory for probabilistic weighted automata: emptiness and universality, expressiveness, and closure under various operations on languages. For quantitative languages, emptiness and universality are defined as whether the value of some (resp. every) word exceeds a given threshold. We prove some of these questions to be decidable, and others undecidable. Regarding expressive power, we show that probabilities allow us to define a wide variety of new classes of quantitative languages, except for discountedsum automata, where probabilistic choice is no more expressive than nondeterminism. Finally, we give an almost complete picture of the closure of various classes of probabilistic weighted automata for the following pointwise operations on quantitative languages: max, min, sum, and numerical complement. 1
Synthesizing systems with optimal averagecase behavior for ratio objectives
 of EPTCS
, 2011
"... We show how to automatically construct a system that satisfies a given logical specification and has an optimal average behavior with respect to a specification with fractional costs. When synthesizing a system from a logical specification, it is often the case that several different systems satisfy ..."
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Cited by 6 (2 self)
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We show how to automatically construct a system that satisfies a given logical specification and has an optimal average behavior with respect to a specification with fractional costs. When synthesizing a system from a logical specification, it is often the case that several different systems satisfy the specification. In this case, it is usually not easy for the user to state formally which system she prefers. Prior work proposed to rank the correct systems by adding a quantitative aspect to the specification. A desired preference relation can be expressed with (i) a quantitative language, which is a function assigning a value to every possible behavior of a system, and (ii) an environment model defining the desired optimization criteria of the system, e.g., worstcase or averagecase optimal. In this paper, we show how to synthesize a system that is optimal for (i) a quantitative language given by an automaton with a fractional cost function, and (ii) an environment model given by a labeled Markov decision process. The objective of the system is to minimize the expected (fractional) costs. The solution is based on a reduction to Markov Decision Processes with extendedfractional cost functions which do not require that the costs in the denominator are strictly positive. We find an optimal strategy for these using a fractional linear program.
Generalized Quantitative Analysis of Metric Transition Systems
"... Abstract. The formalism of metric transition systems, as introduced by de Alfaro, Faella and Stoelinga, is convenient for modeling systems and properties with quantitative information, such as probabilities or time. For a number of applications however, one needs other distances than the pointwise ..."
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Cited by 1 (1 self)
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Abstract. The formalism of metric transition systems, as introduced by de Alfaro, Faella and Stoelinga, is convenient for modeling systems and properties with quantitative information, such as probabilities or time. For a number of applications however, one needs other distances than the pointwise (and possibly discounted) linear and branching distances introduced by de Alfaro et.al. for analyzing quantitative behavior. In this paper, we show a vast generalization of the setting of de Alfaro et.al., to a framework where any of a large number of other useful distances can be applied. Concrete instantiations of our framework hence give e.g. limitaverage, discountedsum, or maximumlead linear and branching distances; in each instantiation, properties similar to the ones of de Alfaro et.al. hold. In the end, we achieve a framework which is not only suitable for modeling different kinds of quantitative systems and properties, but also for analyzing these by using different applicationdetermined ways of measuring quantitative behavior. 1