System modeling is a crucial and essential part of designing modern systems in order to predict systems’ behavior before their deployment. Performance and dependability are typical attributes of interest and their evaluation is considered as an art usually supported by powerful software tools and sophisticated mathematical methods. Service based architectures, Cloud computing, wireless and networked systems are only some of the types of systems, that very often need to be evaluated all together looking for performance and dependability indices and their relationship to SLAs and QoS parameters. The aim of this special issue is to present novel ideas, methods, algorithms, and software tools for in-depth studies of dynamic aspects of dependable fault-tolerant systems.
The papers selected for this special issue on dynamic systems dependability and performance assessment cover some of the important problems that are currently being addressed by the engineering community. Both theoretical and practical aspects have been dealt with by the special issue. Empirical/statistical and simulation/analytical techniques are covered in this issue. All papers submitted for the special issue were reviewed by the experts in the field. According to the referees’ comments and having verified the focus with the theme of the special issue, 8 best papers were selected that we believe well reflect the current research trends on the topic.
The first paper, A Note on Spare Parts and Logistic Optimization with Monte Carlo based System Models, by A. Dubi, S. Khoroshevsky and A. Doron, presents a novel approach to the problem of spare parts allocation optimization. The proposed approach is based on the hybrid Monte Carlo optimization method removing some drawbacks of such technique and guarantees the optimal solution.
The second paper, MDWNsolver: A Framework to Design and Solve Markov Decision Petri Nets, by M. Beccuti, G. Franceschinis and S. Haddad, proposes a new tool, named MDWNsolver, for solving two extensions of the Petri net formalism for high level specification of Markov Decision Processes (MDP): the Markov Decision Petri Net and the Markov Decision Well-formed Net. In order to reduce the complexity of the analysis, the solution engine uses efficient algorithms that take advantage of system symmetries.
The third paper, Markov Modeling Approach for Survivability Analysis of Cellular Networks, by V. Jindal, S. Dharmaraja and K. S. Trivedi, deals with survivability in cellular networks, using Markov chains and stochastic reward nets to compute measures such as call blocking probabilities and excess delay due to failures.
The fourth paper, Stochastic Petri nets with Low Variation Matrix Exponentially Distributed Firing Time, by P. Buchholz, A. Horvath and M. Telek, proposes a new approach for the solution of stochastic Petri nets based on matrix exponential distributions. In particular the authors demonstrate that all kinds of such distributions can be used like phase type distributions in stochastic Petri nets evaluation.
The fifth paper, Optimal Design of Heterogeneous Series-Parallel Systems with Common-Cause Failures, by P. Boddu, L. Xing and F. Azadivar, proposes a technique for evaluating and optimizing the reliability of systems by combining cold and hot standby redundancy to achieve a balance between fast recovery and power conservation in the optimal system design. The proposed method has no limitation on the type of time-to- failure distributions for the system components and also uses genetic algorithm for obtaining the optimal design configuration satisfying some system-level cost constraints.
The sixth paper, Qualitative and Quantitative Modeling of Reliability for Intelligent Water Distribution Networks, by J. Lin and S. Sedigh, proposes an agent-based qualitative model based on UML and a Markov decision process to evaluate the reliability of water distribution networks, a special case of cyber-physical systems. Such models successfully capture the dependence between cyber components and physical components and evaluate the intelligent water distribution networks as a whole. The reliability results are also compared with purely physical systems to support the advantage of cyber infrastructures.
The seventh paper, PARSY: Performance Aware Reconfiguration of Software Systems, by M. Marzolla and R. Mirandola, presents a framework for runtime performance aware reconfiguration of component-based software systems. The basic underlying idea is to selectively degrade and upgrade system components to guarantee that the overall response time does not exceed a predefined threshold. The main assumption is that the user is willing to accept a degraded service within a maximum response time. A monitoring component is used to trigger a reconfiguration whenever the measured response time exceeds the threshold, and a QN model is solved to estimate, at run-time, the response time of various reconfiguration scenarios. The obtained results are used to feed the optimization model whose solution gives the system configuration that maximizes the total utility, while keeping the response time below the threshold.
Lastly, the eighth paper, Dynamic Aspects and Behaviors in System Performance and Reliability Evaluation, by S. Distefano, A. Puliafito, K.S. Trivedi, deals with dynamic reliability aspects and behaviors in component-based systems. Such aspects and behaviors are identified and characterized and thence some possible modeling and solution techniques are discussed. The main goal of this paper is to highlight the importance of adequately evaluating the system reliability, while taking into account dynamic-dependent aspects and behaviors.
We would like to thank all the authors for the patience and cooperation exhibited and we are grateful to all the referees who gave their valuable time to review the papers promptly. We do hope that this special issue will be received enthusiastically by academia, researchers and engineers involved in performance and reliability engineering.
Last but not the least; we would like to thank Prof. Krishna B. Misra, Editor-in-Chief of the International Journal of Performability Engineering, for enthusiastically supporting us in this endeavor.
Salvatore Distefano is currently a post-doctoral researcher at the University of Messina, also collaborating with the Politecnico di Milano. His research interests include performance evaluation, parallel and distributed computing, software engineering, and reliability techniques. During his research activity, he has contributed in the development of several tools such as WebSPN, ArgoPerformance and GS3. He has been involved in several national and international research projects. He is author of more than 70 scientific publications in international journals and conferences. He is an Associate Editor of International Journal of Performability Engineering.
Antonio Puliafito is a full professor of computer engineering at the University of Messina, Italy. His interests include parallel and distributed systems, networking, wireless, and GRID and Cloud computing. He was a referee for the European Community for the projects of the Fourth, Fifth, Sixth, and Seventh Framework Program. He has contributed to the development of the software tools WebSPN, MAP, and ArgoPerformance. He is a coauthor (with R. Sahner and K.S. Trivedi) of the text Performance and Reliability Analysis of Computer Systems: An Example-Based Approach Using the SHARPE Software Package, Kluwer Academic Publishers, New York, USA, 1996.
Kishor S. Trivedi holds the Hudson Chair in the Department of Electrical and Computer Engineering at Duke University, Durham, NC. He has served as a Principal Investigator on various AFOSR, ARO, Burroughs, DARPA, Draper Lab, IBM, DEC, Alcatel, Telcordia, Motorola, NASA, NIH, ONR, NSWC, Boeing, Union Switch and Signals, NSF, and SPC funded projects and as a consultant to industry and research laboratories. He was an Editor of the IEEE Transactions on Computers from 1983-1987. He is on the editorial board of the IEEE Transactions on Dependable and Secure Systems. He is also on the Editorial Board of International Journal of Performability Engineering. He is a co-designer of HARP, SAVE, SHARPE, SPNP, and SREPT modeling packages. He is the author of a well known text entitled, Probability and Statistics with Reliability, Queuing and Computer Science Applications, John Wiley & Sons, New York, USA, 2001. He has published two other books entitled, Performance and Reliability Analysis of Computer Systems: An Example-Based Approach Using the SHARPE Software Package, published by Kluwer Academic Publishers, New York, USA, 1996 and Queuing Networks and Markov Chains, John Wiley, New York, USA, 2006. His interests include stochastic processes, Petri nets, queuing networks, performance /reliability /performability/ survivability analysis and software rejuvenation. He has published over 350 articles and lectured extensively on these topics. He has supervised 39 Ph.D. dissertations. He is a Fellow of the Institute of Electrical and Electronics Engineers. He is a Golden Core Member of IEEE Computer Society.