Expressing best practices in (risk) analysis and testing of safety-critical systems using patterns

The continuing pervasion of our society with safety-critical cyber-physical systems not only demands for adequate (risk) analysis, testing and verification techniques, it also generates growing experience on their use, which can be considered as important as the tools themselves for their efficient use. This paper introduces workflow patterns to describe such best practices in a systematic way that efficiently represents this knowledge, and also provides a way to relate different patterns, making them easier to identify and use, and cover as wide a range of experiences as possible. The value of the approach is demonstrated using some pattern examples from a collection developed in the Artemis-project MBAT. Finally, the paper presents a wiki-based approach for developing and maintaining the pattern collection

Detecting Consistencies and Inconsistencies of Pattern-Based Functional Requirements

The formal specification of functional requirements can often lead to inconsistency as well as unintended specification, especially in the early stages within the development process. In this paper, we present a formal model checking approach which tackles both of these problems and is also applicable during the requirements elicitation phase, in which no component model is available. The presented notion of consistency ensures the existence of at least one possible run of the system, which satisfies all requirements. To avoid trivial execution traces, the "intended" functional behavior of the requirements is triggered. The analysis is performed using model checking. More specifically, to reduce the overall analysis effort, we apply a bounded model checking scheme. If the set of requirements is inconsistent the method also identifies a maximal sub-set of consistent requirements. Alternatively, a minimal inconsistent sub-set can be computed. The approach is demonstrated on a railway crossing example using the BTC Embedded Specifier and the iSAT model checker

Sequence Diagram Test Case Specification and Virtual Integration Analysis using Timed-Arc Petri Nets

In this paper, we formally define Test Case Sequence Diagrams (TCSD) as an easy-to-use means to specify test cases for components including timing constraints. These test cases are modeled using the UML2 syntax and can be specified by standard UML-modeling-tools. In a component-based design an early identification of errors can be achieved by a virtual integration of components before the actual system is build. We define such a procedure which integrates the individual test cases of the components according to the interconnections of a given architecture and checks if all specified communication sequences are consistent. Therefore, we formally define the transformation of TCSD into timed-arc Petri nets and a process for the combination of these nets. The applicability of our approach is demonstrated on an avionic use case from the ARP4761 standard

Feasibility, safety and diagnostic impact of endomyocardial biopsies for the diagnosis of myocardial disease in children and adolescents

AIMS: Endomyocardial biopsies (EMBs) are performed infrequently in children owing to significant past complication rates and controversial discussions about the therapeutic value of results. The objective of this study is to investigate the safety and feasibility of EMBs for suspected myocardial disease in relation to their clinical value. METHODS AND RESULTS: Retrospective multicentre review of the Working Group for Interventional Cardiology of the German Society for Paediatric Cardiology. During 3 consecutive years 206 EMBs (84 female / mean age 8.95±6.62 years) were performed and analysed at 15 heart centres. In the majority of cases biopsies were taken from the right ventricle (RV/ 89.8%; p<0.001). The overall complication rate was 9.7%, whereas major complications occurred in only 0.97% of cases. Risk factors associated with a higher complication rate were biopsy during the first year of life (20.5%) and from the left ventricle (31.1%); (p<0.05). There was no procedure-related mortality. Treatment was changed in 18.0% of cases based on biopsy results. CONCLUSIONS: Today, endomyocardial biopsies in older children with suspected myocardial disease can be performed safely with a low risk of major complications and mortality, whereas the risk of complications if the biopsy is carried out in the first year of life or taken from the left ventricle remains high