Stochastic model checking is a recent extension of traditional modelchecking techniques for the integrated analysis of both qualitative and quantitative system properties. In this paper we show how stochastic model checking can be conveniently used to address a number of usability concerns that involve quantitative aspects of a user interface for the industrial groupware system thinkteam. thinkteam is a ready-to-use Product Data Management application developed by think3. It allows enterprises to capture, organise, automate, and share engineering product information and it is an example of an asynchronous and dispersed groupware system. Several aspects of the functional correctness, such as concurrency aspects and awareness aspects, of the groupware protocol underlying thinkteam and of its planned publish/subscribe notification service have been addressed in previous work by means of a traditional model-checking approach. In this paper we investigate the trade-off between two different design options for granting users access to files in the database: a retrial approach and a waiting-list approach and show how stochastic model checking can be used for such analyses.

Abstract. We consider infinite-state discrete Markov chains which are eager: the probability of avoiding a defined set of final states for more thanÒsteps is bounded by some exponentially decreasing function�(Ò). We prove that eager Markov chains include those induced by Probabilistic Lossy Channel Systems, Probabilistic Vector Addition Systems with States, and Noisy Turing Machines, and that the bounding function�(Ò) can be effectively constructed for them. Furthermore, we study the problem of computing the expected reward (or cost) of runs until reaching the final states, where rewards are assigned to individual runs by computable reward functions. For eager Markov chains, an effective path exploration scheme, based on forward reachability analysis, can be used to approximate the expected reward up-to an arbitrarily small error. 1

The programming and modeling language Klaim has been designed to address key functional aspects of global computing such as distribution awareness, (code and agent) mobility, and privacy aspects. This paper concentrates on their integration with performance and dependability aspects, the logical characterization of performance and dependability requirements, and the automatic validation of system models against integrated formal functional and performance/dependability requirements. To that purpose the temporal logic MoSL is introduced for formulating properties of models specified in StoKlaim, a Markovian extension of Klaim introduced in previous work of the authors. MoSL is inspired by (an action-based version of) CSL, an extension of CTL with ample means to refer to performance and dependability aspects. It is shown that a substantial fragment of the logic can be mapped onto the input language of existing probabilistic model checkers, thus allowing for the automated verification of qualitative and quantitative properties of network-aware programs. The approach is illustrated by modeling and verifying the spreading of a virus through a network.

We consider discrete infinite-state Markov chains which contain an eager finite attractor. A finite attractor is a finite subset of states that is eventually reached with probability 1 from every other state, and the eagerness condition requires that the probability of avoiding the attractor in n or more steps after leaving it is exponentially bounded in n. Examples of such Markov chains are those induced by probabilistic lossy channel

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Mueller (Kaiserslautern University), Bernd Reuther (Kaiserslautern University),

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Foreword CaberNet 1 is the Network of Excellence (NoE) in distributed and dependable systems. It is funded by the

This document presents a CaberNet vision of Research and Technology Development (RTD) in Distributed and Dependable systems. It takes as a basis the state-of-the-art (SOTA) Report prepared by John Bates in 1998: this document was commissioned by CaberNet as a first step towards the definition of a roadmap for European research in distributed and dependable systems. This report overviewed the developments in the main areas to which the CaberNet members made outstanding contributions, which were the most important at the time of its preparation, and analysed the most important trends in R&D in those areas

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