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Critical infrastructures (CI) such as telecommunication or the power grids and their dependencies are getting increasingly complex. Understanding these -often indirectdependencies is a vital precondition for the prevention of crosssector cascading failures of CI. Simulation is an important tool for CI dependency analysis, the test of methods for risk reduction, and as well for the evaluation of past failures. Moreover, interaction of such simulations with external threat models, e.g., a river flood model and economic models, may assist in what-if decision-making processes. The simulation of complex scenarios involving several different CI sectors requires the usage of heterogeneous federated simulations of CI. However, common standards for modelling and interoperability of such federated CI simulations are missing. In this paper, we present a novel approach for coupling CI simulations, developed and realised in the EU project DIESIS. The DIESIS core technologies for coupling CI simulations include a middleware that enables semantic interoperability of the federate simulators, a systematic, service-oriented approach to set up and run such federations, and, most importantly, a scenario-based architecture concept for modelling and federated simulation of CI. The architecture foresees a flexible pair-wise (lateral) coupling of simulators. DIESIS has implemented a demonstrator as a proof of concept for its approach and technologies, by coupling four different simulation systems (three interacting CIs and an external, common threat). In this paper, we focus on the architectural concept and the interoperability middleware that realises this concept and allows the coupling of heterogeneous simulation systems using various time and data models. We show how the ontology-based Knowledge Based System (KBS) is integrated and used in the overall system. Then, we discuss the basic technical concepts as well as the results obtained with the demonstrator. The proposed architecture is open for further extensions. Ultimately, the proposed approach shall form the basis of a future standard coupling middleware for federated CI simulations.

This paper describes the basic components of the L3 operating system and the experiences of the first two years using it. The system results from scientific research, but is addressed to commercial application. It is based on a small kernel handling tasks, threads and dataspaces. User level device drivers and file systems are described as examples of flexible OS services realized outside the kernel.

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Edited by Brian HamblingThis best-selling software testing title explains the basic steps of software testing and how to perform effective tests. It is the only official textbook of the ISTQB-BCS Certified Tester Foundation Level, with self-assessment exercises, guidance notes on the syllabus topics and sample examination questions. 'This book covers all the sections of the latest 2018 CTFL syllabus and more. It is not just written as an exam aid though, it is a reference for software testing in its own right...for anyone involved in the development of software, whatever development methodology the project follows. '