Miroslaw Malek

Current solutions for Web service composition

Web service composition lets developers create applications on top of service-oriented computings native description, discovery, and communication capabilities. Such applications are rapidly deployable and offer developers reuse possibilities and users seamless access to a variety of complex services. There are many existing approaches to service composition, ranging from abstract methods to those aiming to be industry standards. The authors describe four key issues for Web service composition.

The consensus problem in fault-tolerant computing

The consensus problem is concerned with the agreement on a system status by the fault-free segment of a processor population in spite of the possible inadvertent or even malicious spread of disinformation by the fault segment of that population. The resulting protocols are useful throughout fault-tolerant distributed systems and will impact the design of other decision systems to come. This paper surveys research on the consensus problem, compares approaches, outlines applications, and suggests directions for future work.

A survey of online failure prediction methods

With the ever-growing complexity and dynamicity of computer systems, proactive fault management is an effective approach to enhancing availability. Online failure prediction is the key to such techniques. In contrast to classical reliability methods, online failure prediction is based on runtime monitoring and a variety of models and methods that use the current state of a system and, frequently, the past experience as well. This survey describes these methods. To capture the wide spectrum of approaches concerning this area, a taxonomy has been developed, whose different approaches are explained and major concepts are described in detail.

A comparison connection assignment for diagnosis of multiprocessor systems

A comparison method for diagnosis of multiprocessor systems is introduced. Given a system of n units modeled by a linear graph, problems of finding the minimum number of comparison edges required for fault detection and fault location are solved by the use of a covering algorithm. The bounds for the number of comparison edges, the number of necessary comparisons and test cycles in fault detection and fault location in systems with n units are determined and an algorithm for an optimal comparison connection assignment is given. Simplicity and ease of implementation make the described method applicable for fault detection and location in multiprocessor systems.

Survey of software tools for evaluating reliability, availability, and serviceability

In computer design, it is essential to know the effectiveness of different design options in improving performance and dependability. Various software tools have been created to evaluate these parameters, applying both analytic and simulation techniques, and this paper reviews those related primarily to reliability, availability, and serviceability. The purpose, type of models used, type of systems modeled, inputs, and outputs are given for each package. Examples of some of the key modeling elements such as Markov chains, fault trees, and Petri nets are discussed. The information is compiled to facilitate recognition of similarities and differences between various models and tools and can be used to aid in selecting models and tools for a particular application or designing tools for future needs. Tools included in the evaluation are CARE-III, ARIES-82, SAVE, MARKl, HARP, SHARPE, GRAMP, SURF, SURE, ASSIST, METASAN, METFAC, ARM, and SUPER. Modeling tools, such as REL70, RELCOMP, CARE, CARSRA, and CAST, that were forerunners to some of the current tools are noted for their contributions. Modeling elements that have gained widespread use for general systems, as well as fault-tolerant systems, are included. Tools capable of modeling both repairable and nonrepairable systems, accepting constant or time varying failure rates, and predicting reliability, availability, and serviceability parameters are surveyed.

Serial and parallel simulated annealing and tabu search algorithms for the traveling salesman problem

This paper describes serial and parallel implementations of two different search techniques applied to the traveling salesman problem. A novel approach has been taken to parallelize simulated annealing and the results are compared with the traditional annealing algorithm. This approach uses abbreviated cooling schedule and achieves a superlinear speedup. Also a new search technique, called tabu search, has been adapted to execute in a parallel computing environment. Comparison between simulated annealing and tabu search indicate that tabu search consistently outperforms simulated annealing with respect to computation time while giving comparable solutions. Examples include 25, 33, 42, 50, 57, 75 and 100 city problems.

A fault-tolerant FFT processor

A method is proposed for achieving fault tolerance by introducing a redundant stage for a special-purpose fast Fourier transform (FFT) processor. A concurrent error-detection technique, called recomputing by alternate path, is used to detect errors during normal operation. Once an error is detected, a faulty butterfly can be located with log (N+5) additional cycles. The method has 100% detection and location capability, regardless of the magnitude of the roundoff errors. A gracefully degraded reconfiguration using a redundant stage is introduced. This technique ensures a high improvement in reliability and availability. Hardware overhead is O(1/log N) with some additional comparators and switches. The method can be applied to other algorithms implementable on the butterfly structure. >

Using Hidden Semi-Markov Models for Effective Online Failure Prediction

A proactive handling of faults requires that the risk of upcoming failures is continuously assessed. One of the promising approaches is online failure prediction, which means that the current state of the system is evaluated in order to predict the occurrence of failures in the near future. More specifically, we focus on methods that use event-driven sources such as errors. We use hidden semi-Markov models (HSMMs)for this purpose and demonstrate effectiveness based on field data of a commercial telecommunication system. For comparative analysis we selected three well-known failure prediction techniques: a straightforward method that is based on a reliability model, dispersion frame technique by Lin and Siewiorek and the eventset-based method introduced by Vilalta et al. We assess and compare the methods in terms of precision, recall, F-measure, false-positive rate, and computing time. The experiments suggest that our HSMM approach is very effective with respect to online failure prediction.

A fault-tolerant systolic sorter

A fault-tolerant systolic sorter design is proposed. An algorithm-based fault tolerance is achieved by testing the invariants of a systolic sorter during normal operation. Transient and permanent computation errors can be detected by using error-checking code and some redundant cells. A block with a single faulty cell can be located. Small hardware overhead and negligible time overhead are shown to be the major advantages of the method. A hierarchical structure is suggested as an efficient architecture for realizing the method. An offline fault-testing method for permanent stuck-at faults is presented. >

Routing and security in mobile ad hoc networks

Mobile ad hoc networks remove the dependence on a fixed network infrastructure by treating every available mobile node as an intermediate switch, thereby extending the range of mobile nodes well beyond that of their base transceivers. We present four manet routing algorithms along with a hybrid approach, discuss their advantages and disadvantages, and describe security problems inherent in such networks.