Wojciech Zamojski

Complex Systems and Dependability

Typical contemporary complex system is a multifaceted amalgamation of technical, information, organization, software and human (users, administrators and management) resources. Complexity of such a system comes not only from its involved technical and organizational structure but mainly from complexity of information processes that must be implemented in the operational environment (data processing, monitoring, management, etc.). In such case traditional methods of reliability analysis focused mainly on technical level are usually insufficient in performance evaluation and more innovative methods of dependability analysis must be applied which are based on multidisciplinary approach to theory, technology and maintenance of systems operating in real (and very often unfriendly) environments. This monograph presents selected new developments in such areas of dependability research as system modelling, tools and methodologies for system analysis, data security, secure system design and specific dependability aspects in specialized technical applications. Many practical cases illustrate the universal rule that complexity and multiplicity of system processes, their concurrency and their reliance on embedded intelligence (human and artificial) significantly impedes construction of strict mathematical models and calls for application of intelligent and soft computing methods.

New Results in Dependability and Computer Systems

DepCoS RELCOMEX is an annual series of conferences organized by the Institute of Computer Engineering, Control and Robotics (CECR), Wrocaw University of Technology, since 2006. Its idea came from the heritage of the other two cycles of events: RELCOMEX Conferences (1977 89) and Microcomputer Schools (1985 95) which were then organized by the Institute of Engineering Cybernetics, the previous name of CECR. In contrast to those preceding meetings focused on the conventional reliability analysis, the DepCoS mission is to develop a more comprehensive approach to computer system performability, which is now commonly called dependability. Contemporary technical systems are integrated unities of technical, information, organization, software and human resources. Diversity of the processes being realized in the system, their concurrency and their reliance on in-system intelligence significantly impedes construction of strict mathematical models and calls for application of intelligent and soft computing methods. The submissions included in this volume illustrate variety of problems that need to be explored in the dependability analysis: methodologies and practical tools for modeling, design and simulation of the systems, security and confidentiality in information processing, specific issues of heterogeneous, today often wireless, computer networks, or management of transportation networks.

Calculation of the internal thermal resistance and ampacity of 3-core unscreened cables with fillers

All 3-core cables require fillers to fill the space between insulated cores and the belt insulation or a sheath. The equations given in IEC 287 and in the Neher-McGrath paper (1957) for the internal thermal resistance of 3-core cables were developed for paper insulated cables. For such cables, it was assumed that the insulation and filler materials have the same thermal resistivities. In reality, in 3-core cables a variety of materials are used as fillers. The majority of these will have a higher thermal resistivity than the insulation. In the previous paper, a new formula was developed to compute the value of the internal thermal resistance of belted cables taking into account the thermal resistivity of the filler. In this paper, screened cables are considered and a new formula for the computation of the internal thermal resistance of such cables is presented. The effect of filler resistivity on cable ampacity is also discussed.

Introduction to the Dependability Modeling of Computer Systems

Computer systems and networks are considered as a union of all resources, i.e. hardware, software and people (users, administrators and managers), essential for the realization of predicted tasks. The system dependability is defined as a generalization of performability and reliability, combining the notions of both these terms. The functional-reliability models are based on the observation that only a subset of the system resources is involved in a task execution and only inefficiencies of these resources may influence the correctness of task realization. The systems are working in a real environment, which is often hostile: it may be a source of threats, such as security intrusions, faulty or modified software and human errors. The set of analyzed events is a sum of hardware failures and malfunctions, software faults, human errors, intrusions (intended and addressed threats), and viruses (unaddressed threats that are broadcast in the system and in its environment)

Theory and Engineering of Complex Systems and Dependability

Building upon a long tradition of scientifi c conferences dealing with problems ofreliability in technical systems, in 2006 Department of Computer Engineering atWrocaw University of Technology established DepCoS-RELCOMEX series of eventsin order to promote a comprehensive approach to evaluation of system performabilitywhich is now commonly called dependability.Contemporary complex systems integrate variety of technical, information, soft wareand human (users, administrators and management) resources. Their complexitycomes not only from involved technical and organizational structures but mainly fromcomplexity of information processes that must be implemented in specific operationalenvironment (data processing, monitoring, management, etc.). In such a case traditionalmethods of reliability evaluation focused mainly on technical levels are insufficient andmore innovative, multidisciplinary methods of dependability analysis must be applied.Selection of submissions for these proceedings exemplify diversity of topics that mustbe included in such analyses: tools, methodologies and standards for modelling,design and simulation of the systems, security and confidentiality in informationprocessing, specific issues of heterogeneous, today often wireless, computer networks,or management of transportation networks. In addition, this edition of the conferencehosted the 5th CrISS-DESSERT Workshop devoted to the problems of security andsafety in critical information systems.

Mobile object localisation based on acoustic information

The paper considers an acoustic method to localise objects based on sound emitted by them. The localisation algorithm uses two audible signals provided by microphones placed some distance off. The signals received by microphones are analysed using cross-correlation techniques to calculate the difference of signal paths from an object to each microphone. The calculated difference is converted to an angle which describes the actual direction of an object. The paper includes the theoretical basis, methods and the results of the realised experiment for logged real audible signals emitted by mobile objects. The localisation algorithm was implemented as a computer program which uses a DSP processor and warrants the real-time processing. Results of localisation of various military vehicles are also presented.

Proceedings of the Ninth International Conference on Dependability and Complex Systems DepCoS-RELCOMEX. June 30 – July 4, 2014, Brunów, Poland

Writing real world distributed applications is a challenging task. Even if well known models or powerful frameworks such as MapReduce or HADOOP are employed, the complexity of the aspects involved, such as specific programming and data models, deployment scripts or a hard debugging process are enough to require many working hours or even make the entire process unsuitable for practical purposes. For applications which need some of their own components to be computed in a distributed manner, a generic model incurs an unnecessary overhead and makes the whole development slower. We propose a MapReduce framework which automatically handles all the distributed computing tasks such as computing resources abstraction, code deployment, objects serialization, remote invocations and synchronizations with only a minimal coding overhead. With only minimal constructions dependable distributed components can be developed and run on heterogeneous platforms and networks. The presented results confirm the performance of the proposed method.

Dependability Analysis of Information Systems with Hierarchical Reconfiguration of Services

The paper presents an approach to dependability analysis of a class of networked information systems based on distributed services. The system consists of groups of servers that react autonomously to detected events, component failures and security incidents. These local reactions affect the availability of the services, provided by the system, then restored by reconfiguration. The dependability analysis is based on the construction of a reconfiguration graph, which is transformed to a state-transition dependability model.

Dependability Engineering and Complex Systems

These proceedings present the results of the Eleventh International Conference on Dependability and Complex Systems DepCoS-RELCOMEX which took place in a picturesque Brunow Palace in Poland from 27th June to 1st July, 2016. DepCoS-RELCOMEX is a series of international conferences organized annually by Department of Computer Engineering of Wroclaw University of Science and Technology since 2006. The roots of the series go as far back as to the seventies of the previous century the first RELCOMEX conference took place in 1977 and now its main aim is to promote a multi-disciplinary approach to dependability problems in theory and engineering practice of complex systems. Complex systems, nowadays most often computer-based and distributed, are built upon a variety of technical, information, software and human resources. The challenges in their design, analysis and maintenance not only originate from the involved technical and organizational structures but also from the complexity of the information processes that must be efficiently executed in a diverse, often hostile operational environment. Traditional methods of reliability evaluation focused only on technical resources are usually insufficient in this context and more innovative, multidisciplinary methods of dependability analysis must be applied. The diversity of the topics which need to be considered is well illustrated by the selection of the submissions in these proceedings with their subjects ranging from mathematical models and design methodologies through software engineering and data security issues up to practical problems in technical, e.g. transportation, systems

Functional-Reliability Model of a Services System with Path Reconfiguration Ability

In this work we analyse operation of a services network which is built from processing nodes serving dedicated services and communication links transmitting required information resources. For task executions specific subsets of network resources – so called communication paths – are allocated. Execution of a task in communication paths is disrupted by occurring faults which are eliminated by renewal procedures leading to delays in task completion time or even to task cancellation. One of the method for overcoming the negative effects of the faults is to apply a path reconfiguration mechanism i.e. a redirection of the communication traffic which bypasses the damaged link. We propose a functional-reliability dependability model of the services network which takes into account possible path reconfigurations. We also define a network dependability parameter which evaluates network efficiency by finding the degree of task losses among all the jobs being executed in the network.