QuantUM: Quantitative Safety Analysis of UML Models

When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system architects to integrate these techniques into their every day work. This is mainly due to the lack of methods that can be directly applied to architecture level models, for instance given as UML diagrams. Also, it is necessary that the description methods used do not require a profound knowledge of formal methods. Our approach bridges this gap and improves the integration of quantitative safety analysis methods into the development process. All inputs of the analysis are specified at the level of a UML model. This model is then automatically translated into the analysis model, and the results of the analysis are consequently represented on the level of the UML model. Thus the analysis model and the formal methods used during the analysis are hidden from the user. We illustrate the usefulness of our approach using an industrial strength case study.Comment: In Proceedings QAPL 2011, arXiv:1107.074

Model exploration and analysis for quantitative safety refinement in probabilistic B

The role played by counterexamples in standard system analysis is well known; but less common is a notion of counterexample in probabilistic systems refinement. In this paper we extend previous work using counterexamples to inductive invariant properties of probabilistic systems, demonstrating how they can be used to extend the technique of bounded model checking-style analysis for the refinement of quantitative safety specifications in the probabilistic B language. In particular, we show how the method can be adapted to cope with refinements incorporating probabilistic loops. Finally, we demonstrate the technique on pB models summarising a one-step refinement of a randomised algorithm for finding the minimum cut of undirected graphs, and that for the dependability analysis of a controller design.Comment: In Proceedings Refine 2011, arXiv:1106.348

Argentine Wheat Industry: Conference Report

Established and supported under the Australian Government’s Cooperative Research Centre Progra

DiPro- A Tool for Probabilistic Counterexample Generation

Abstract. The computation of counterexamples for probabilistic model checking has been an area of active research over the past years. In spite of the achieved theoretical results in this field, there is no freely available tool that allows for the computation and representation of probabilistic counterexamples. We present an open source tool called DiPro that can be used with the PRISM and MRMC probabilistic model checkers. It allows for the computation of probabilistic counterexamples for discrete time Markov chains (DTMCs), continuous time Markov chains (CTMCs) and Markov decision processes (MDPs). The computed counterexamples can be rendered graphically.

A user-study examining visualization of lifelogs

With continuous advances in the pervasive sensing and lifelogging technologies for the quantified self, users now can record their daily life activities automatically and seamlessly. In the existing lifelogging research, visualization techniques for presenting the lifelogs and evaluating the effectiveness of such techniques from a lifelogger's perspective has not been adequately studied. In this paper, we investigate the effectiveness of four distinct visualization techniques for exploring the lifelogs, which were collected by 22 lifeloggers who volunteered to use a wearable camera and a GPS device simultaneously, for a period of 3 days. Based on a user study with these 22 lifeloggers, which required them to browse through their personal lifelogs, we seek to identify the most effective visualization technique. Our results suggest various ways to augment and improve the visualization of personal lifelogs to enrich the quality of user experience and making lifelogging tools more engaging. We also propose a new visualization feature-drill-down approach with details-on-demand, to make the lifelogging visualization process more meaningful and informative to the lifeloggers

From probabilistic counterexamples via causality to fault trees

Abstract. In recent years, several approaches to generate probabilistic counterexamples have been proposed. The interpretation of stochastic counterexamples, however, continues to be problematic since they have to be represented as sets of paths, and the number of paths in this set may be very large. Fault trees (FTs) are a well-established industrial technique to represent causalities for possible system hazards resulting from system or system component failures. In this paper we suggest a method to automatically derive FTs from counterexamples, including a mapping of the probability information onto the FT. We extend the structural equation approach by Pearl and Halpern, which is based on Lewis counterfactuals, so that it serves as a justification for the causality that our proposed FT derivation rules imply. We demonstrate the usefulness of our approach by applying it to an industrial case study.

Safety Analysis of an Airbag System using Probabilistic FMEA and Probabilistic Counterexamples

Abstract—Failure mode and effects analysis (FMEA) is a technique to reason about possible system hazards that result from system or system component failures. Traditionally, FMEA does not take the probabilities with which these failures may occur into account. Recently, this shortcoming was addressed by integrating stochastic model checking techniques into the FMEA process. A further improvement is the integration of techniques for the generation of counterexamples for stochastic models, which we propose in this paper. Counterexamples facilitate the redesign of a potentially unsafe system by providing information which components contribute most to the failure of the entire system. The usefulness of this novel approach to the FMEA process is illustrated by applying it to the case study of an airbag system provided by our industrial partner, the TRW Automotive GmbH. I

Fragmentation of alkoxy radicals: Mechanistic aspects of the tandemβ-fragmentation-intramolecular functionalization reaction

4 pages, 1 figure, 1 table, 1 scheme.The formation of the β-peroxylactone (4) during the photolysis of lactol (3) with (diacetoxyiodo)-benzene (DIB) and iodine under oxygen atmosphere demostrates the presence of a peroxyradical intermediate in the tandem β-fragmentation-intramolecular functionalization reaction.This work was supported by the Investigation Programme of the Comisión Asesora de Investigación Científica y Técnica. We thank the Instituto de Cooperación Iberoamericana for a fellowship (to J.J.M.)