Symblicit algorithms for optimal strategy synthesis in monotonic Markov decision processes

When treating Markov decision processes (MDPs) with large state spaces, using explicit representations quickly becomes unfeasible. Lately, Wimmer et al. have proposed a so-called symblicit algorithm for the synthesis of optimal strategies in MDPs, in the quantitative setting of expected mean-payoff. This algorithm, based on the strategy iteration algorithm of Howard and Veinott, efficiently combines symbolic and explicit data structures, and uses binary decision diagrams as symbolic representation. The aim of this paper is to show that the new data structure of pseudo-antichains (an extension of antichains) provides another interesting alternative, especially for the class of monotonic MDPs. We design efficient pseudo-antichain based symblicit algorithms (with open source implementations) for two quantitative settings: the expected mean-payoff and the stochastic shortest path. For two practical applications coming from automated planning and LTL synthesis, we report promising experimental results w.r.t. both the run time and the memory consumption.Comment: In Proceedings SYNT 2014, arXiv:1407.493

Supporting ODP - Translating LOTOS to Z

This paper describes a translation of full LOTOS into Z. A common semantic model is defined and the translation is proved correct with respect to the semantics. The motivation for such a translation is the use of multiple viewpoints for specifying complex systems defined by the reference model of the Open Distributed Processing (ODP) standardization initiative. The postscript version available here is an extended version of what was published

A symbolic semantics for a clculus for service-oriented computing

We introduce a symbolic characterisation of the operational semantics of COWS, a formal language for specifying and combining service-oriented applications, while modelling their dynamic behaviour. This alternative semantics avoids infinite representations of COWS terms due to the value-passing nature of communication in COWS and is more amenable for automatic manipulation by analytical tools, such as e.g. equivalence and model checkers. We illustrate our approach through a ‘translation service’ scenario

Meta SOS - A Maude Based SOS Meta-Theory Framework

Meta SOS is a software framework designed to integrate the results from the meta-theory of structural operational semantics (SOS). These results include deriving semantic properties of language constructs just by syntactically analyzing their rule-based definition, as well as automatically deriving sound and ground-complete axiomatizations for languages, when considering a notion of behavioural equivalence. This paper describes the Meta SOS framework by blending aspects from the meta-theory of SOS, details on their implementation in Maude, and running examples.Comment: In Proceedings EXPRESS/SOS 2013, arXiv:1307.690

New developments around the μCRL tool set1 1http://www.cwi.nl/~mcrl

AbstractSome recent developments in the μCRL tool set are presented. New analysis techniques are a symbolic model checker, and a visualizer for huge state spaces. Also various transformations are presented. At symbolic level, theorem proving, data flow analysis, and confluence checking are used to obtain considerable state space reductions. At the concrete level, distributed implementations of state space generation and minimization are recent. We mention the successful application of the tools to the verification of large data-intensive distributed systems

Bisimulation symbolique pour les systèmes ouverts et paramétrés - Version étendue

Les automates ouverts(OA) sont des modèles symboliques et paramétrés pour les systèmes concurrents ouverts. Ici,ouvert désigne des systèmes partiellement spécifiés, qui peuvent être instanciés ou assemblés pour construire de plus grands systèmes. Une propriété importante pour de tels systèmes est la "compositionnalité", ce qui signifie que les propriétés logiques et les équivalences peuvent être vérifiées localement et seront préservées par la composition. Dans des travaux antérieurs, une notion d’équivalence nommée FH-Bisimulationa été définie pour les automates ouverts et se révélait être une congruence pour leur composition. Mais cette équivalence a été définie pour une variante des automates ouverts intrinsèquement infinis,ce qui la rend impropre au traitement algorithmique.Nous définissons une nouvelle forme d’équivalence nommée StrFH-Bisimulation, travaillant sur des codages finis des OA. Nous prouvons que la StrFH-Bisimulation est cohérente et complète pour la FH-Bisimulation.Nous proposons ensuite deux algorithmes pour vérifier StrFH-Bisimulation: le premier re-quiert une relation (définie par l’utilisateur) entre les états de deux OA finis, et vérifie s’il s’agit d’une strFH-Bisimulation. La seconde prend deux AO finies en entrée et construit une "StrFH-bisimulation la plus faible" telle que leurs états initiaux soient bisimilaires. Nous prouvons que cet algorithme termine lorsque les domaines de données sont finis. Les deux algorithmes utilisent un solveur SMT comme base pour résoudre les obligations de preuve