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1 COSMOS: a Statistical Model Checker for the Hybrid Automata Stochastic Logic
"... Abstract—This tool paper introduces COSMOS, a statistical model checker for the Hybrid Automata Stochastic Logic (HASL). HASL employs Linear Hybrid Automata (LHA), a generalization of Deterministic Timed Automata (DTA), to describe accepting execution paths of a Discrete Event Stochastic Process (DE ..."
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Abstract—This tool paper introduces COSMOS, a statistical model checker for the Hybrid Automata Stochastic Logic (HASL). HASL employs Linear Hybrid Automata (LHA), a generalization of Deterministic Timed Automata (DTA), to describe accepting execution paths of a Discrete Event Stochastic Process (DESP), a class of stochastic models which includes, but is not limited to, Markov chains. As a result HASL verification turns out to be a unifying framework where sophisticated temporal reasoning is naturally blended with elaborate rewardbased analysis. COSMOS takes as input a DESP (described in terms of a Generalized Stochastic Petri Net), an LHA and an expression Z representing the quantity to be estimated. It returns a confidence interval estimation of Z. COSMOS is written in C++ and is freely available to the research community. I.
C.: Coupling and importance sampling for statistical model checking. Research Report LSV1201, Laboratoire Spécification et Vérification. ENS
, 2012
"... Abstract. Statistical modelchecking is an alternative verification technique applied on stochastic systems whose size is beyond numerical analysis ability. Given a model (most often a Markov chain) and a formula, it provides a confidence interval for the probability that the model satisfies the for ..."
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Cited by 9 (4 self)
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Abstract. Statistical modelchecking is an alternative verification technique applied on stochastic systems whose size is beyond numerical analysis ability. Given a model (most often a Markov chain) and a formula, it provides a confidence interval for the probability that the model satisfies the formula. One of the main limitations of the statistical approach is the computation time explosion triggered by the evaluation of very small probabilities. In order to solve this problem we develop a new approach based on importance sampling and coupling. The corresponding algorithms have been implemented in our tool COSMOS. We present experimentation on several relevant systems, with estimated time reductions reaching a factor of 10 −120.
CosyVerif: an Open Source Extensible Verification Environment
"... Abstract—CosyVerif aims at gathering within a common framework various existing tools for specification and verification. It has been designed in order to 1) support different formalisms with the ability to easily create new ones, 2) provide a graphical user interface for every formalism, 3) include ..."
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Cited by 4 (3 self)
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Abstract—CosyVerif aims at gathering within a common framework various existing tools for specification and verification. It has been designed in order to 1) support different formalisms with the ability to easily create new ones, 2) provide a graphical user interface for every formalism, 3) include verification tools called via the graphical interface or via an API as a Web service, and 4) offer the possibility for a developer to integrate his/her own tool without much effort, also allowing it to interact with the other tools. Several tools have already been integrated for the formal verification of (extensions of) Petri nets and timed automata.
Importance Sampling for Model Checking of Continuous Time Markov Chains
"... Abstract—Model checking real time properties on probabilistic systems requires computing transient probabilities on continuous time Markov chains. Beyond numerical analysis ability, a probabilistic framing can only be obtained using simulation. This statistical approach fails when directly applied t ..."
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Abstract—Model checking real time properties on probabilistic systems requires computing transient probabilities on continuous time Markov chains. Beyond numerical analysis ability, a probabilistic framing can only be obtained using simulation. This statistical approach fails when directly applied to the estimation of very small probabilities. Here combining the uniformization technique and extending our previous results, we design a method which applies to continuous time Markov chains and formulas of a timed temporal logic. The corresponding algorithm has been implemented in our tool COSMOS. We present experimentations on a relevant system. Our method produces a reliable confidence interval with respect to classical statistical model checking on rare events. Keywordsstatistical model checking; rare events; importance sampling; coupling; uniformization I.
Expressive Statistical Model Checking of Genetic Networks with Delayed Stochastic Dynamics
 COMPUTATIONAL METHODS IN SYSTEMS BIOLOGY, UNITED KINGDOM
, 2012
"... The recently introduced Hybrid Automata Stochastic Logic (HASL) [8] establishes a powerful framework for the analysis of a broad class of stochastic processes, namely Discrete Event Stochastic Processes (DESPs). Here we demonstrate the potential of HASL based verification in the context of genetic ..."
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Cited by 1 (0 self)
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The recently introduced Hybrid Automata Stochastic Logic (HASL) [8] establishes a powerful framework for the analysis of a broad class of stochastic processes, namely Discrete Event Stochastic Processes (DESPs). Here we demonstrate the potential of HASL based verification in the context of genetic circuits. To this aim we consider the analysis of a model of gene expression with delayed stochastic dynamics, a class of systems whose dynamics includes both Markovian and nonMarkovian events. We identify a number of relevant properties related to this model, formally express them in HASL terms and, assess them with COSMOS, a statistical model checker for HASL model checking. We demonstrate that this allows assessing the “performances” of a biological system beyond the capability of other stochastic logics.
Statistical Model Checking
, 2012
"... Abstract. Statistical modelchecking is an alternative verification technique applied on stochastic systems whose size is beyond numerical analysis ability. Given a model (most often a Markov chain) and a formula, it provides a confidence interval for the probability that the model satisfies the for ..."
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Abstract. Statistical modelchecking is an alternative verification technique applied on stochastic systems whose size is beyond numerical analysis ability. Given a model (most often a Markov chain) and a formula, it provides a confidence interval for the probability that the model satisfies the formula. One of the main limitations of the statistical approach is the computation time explosion triggered by the evaluation of very small probabilities. In order to solve this problem we develop a new approach based on importance sampling and coupling. The corresponding algorithms have been implemented in our tool COSMOS. We present experimentation on several relevant systems, with estimated time reductions reaching a factor of 10 −120.
Petri Nets Compositional Modeling and Verification of Flexible Manufacturing Systems
"... Flexible Manufacturing Systems (FMS) are amongst the most studied types of systems, however due to their increasing complexity, there is still room for improvement in their modeling and analysis. In this paper we consider the design and the analysis of stochastic models of FMS in two complementary ..."
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Flexible Manufacturing Systems (FMS) are amongst the most studied types of systems, however due to their increasing complexity, there is still room for improvement in their modeling and analysis. In this paper we consider the design and the analysis of stochastic models of FMS in two complementary respects. First we describe a (stochastic) Petri Nets based compositional framework which enables to model an FMS by combination of an arbitrary number of basic components. Second we demonstrate how classical transientanalysis of manufacturing systems, including reliability and performability analysis, can be enriched by application of a novel, sophisticated stochastic logic, namely the Hybrid Automata Stochastic Logic (HASL). We demonstrate the proposed methodology on an FMS example.
FML: Formalism Markup Language
, 2014
"... Many tools for distributed systems verification Relying on different formalisms Solving different problems Applying formal methods to dedicated cases studies Running on different OS Requiring some difficult installation procedures Technological transfer to industry uneasy Étienne André (Paris 13) Th ..."
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Many tools for distributed systems verification Relying on different formalisms Solving different problems Applying formal methods to dedicated cases studies Running on different OS Requiring some difficult installation procedures Technological transfer to industry uneasy Étienne André (Paris 13) The CosyVerif Platform 11th December 2014 2 / 32
Simulationbased Verification of Hybrid Automata Stochastic Logic Formulas for Stochastic Symmetric Nets
"... The Hybrid Automata Stochastic Logic (HASL) has been recently defined as a flexible way to express classical performance measures as well as more complex, pathbased ones (generically called “HASL formulas”). The considered paths are executions of Generalized Stochastic Petri Nets (GSPN), which are ..."
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The Hybrid Automata Stochastic Logic (HASL) has been recently defined as a flexible way to express classical performance measures as well as more complex, pathbased ones (generically called “HASL formulas”). The considered paths are executions of Generalized Stochastic Petri Nets (GSPN), which are an extension of the basic Petri net formalism to define discrete event stochastic processes. The computation of the HASL formulas for a GSPN model is demanded to the COSMOS tool, that applies simulation techniques to the formula computation. Stochastic Symmetric Nets (SSN) are a high level Petri net formalism, of the colored type, in which tokens can have an identity, and it is well known that colored Petri nets allow one to describe systems in a more compact and parametric form than basic (uncolored) Petri nets. In this paper we propose to extend HASL and COSMOS to support colors, so that performance formulas for SSN can be easily defined and evaluated. This requires a new definition of the logic, to ensure that colors are taken into account in a correct and useful manner, and a significant extension of the COSMOS tool.
Expressing and computing passage time measures of GSPN models with HASL
"... Abstract. Passage time measures specification and computation for Generalized Stochastic Petri Net models have been faced in the literature from different points of view. In particular three aspects have been developed: (1) how to select a specific token (called the tagged token) and measure the di ..."
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Abstract. Passage time measures specification and computation for Generalized Stochastic Petri Net models have been faced in the literature from different points of view. In particular three aspects have been developed: (1) how to select a specific token (called the tagged token) and measure the distribution of the time employed from an entry to an exit point in a subnet; (2) how to specify in a flexible way any condition on the paths of interest to be measured, (3) how to efficiently compute the required distribution. In this paper we focus on the specification and computation of complex passage time measures in (Tagged) GSPNs using the Hybrid Automata Stochastic Logic (HASL) and the statistical model checker COSMOS. By considering GSPN models of two different systems, notably, a flexible manufacturing system and a workflow, we identify a number of relevant performance measures (mainly passagetime distributions), formally express them in HASL terms and assess them by means of the COSMOS tool. The interest from the measures specification point of view is provided by the possibility of setting one or more timers along the paths, and setting the conditions for the paths selection, based on the measured values of such timers. With respect to other specification languages allowing to use timers in the specification of performance measures, HASL provides timers suspension, reactivation, rate change along a path.