Multimedia is gaining ever more importance on the Internet. This increases the need for intelligent and efficient video caches. A promising approach to improve caching efficiency is to adapt videos. With the availability of MPEG-4 it is possible to develop a standard compliant proxy cache that allows fast and efficient adaptation. We propose a modular design for an adaptive MPEG-4 video proxy that supports efficient full and partial video caching in combination with filtering options that are driven by the terminal capabilities of the client. We use the native scalability operations provided by MPEG-4, the MPEG-7 standard to describe the scalability options for a video and the emerging MPEG-21 standard to describe the terminal capabilities. In this paper, we will restrict ourselves to full video caching. The combination of adaptation with MPEG-4, MPEG-7 and client terminal capabilities is to the best of our knowledge unique and will increase the quality of service for end users.

Jacek Blazewicz, Klaus Ecker, Brigitte Plateau and Denis Trystram Springer-Verlag, Berlin ISBN, 2000, 635 pp. ISBN 3-540-66441-6, $119.00 As one would expect any handbook to be, it is rather large, a hardcover with 635 pages. Preparing it also must have been a serious endeavor as it contains contributions from 29 authors who put together 12 chapters covering most important aspects of parallel and distributed processing. While the material is not officially presented in this way we can see it as being divided into two parts. First, after a brief introduction to the state-of-the-art and emerging trends, a broad introduction to the fundamental issues in the theory and practice of parallel computing is presented. In this part we find chapters devoted to design of efficient parallel algorithms, languages for parallel processing, architecture of parallel and distributed systems, parallel operating systems, management of resources in parallel systems, tools for parallel computing viewed from the perspective of performance evaluation, parallel database systems and multimedia object servers and networking aspects of distributed and parallel computing. The second part of the book consists of three chapters devoted to applications. Here we can read about parallel and distributed scientific computing, high performance computing in molecular sciences and multimedia applications for parallel and distributed systems. While I could try to discuss the covered material in more detail, this would not be easy due to the depth, breadth and, especially, density of material covered in each chapter. Suffice to say, that a comprehensive description of issues related to languages for parallel processing is condensed to about 60 pages. Therefore, instead of going into details of each chapter, I will rather say that their authors went to great length to make them very high quality overviews of their sub-area and their effort should be appreciated. As a result we obtain a solid summary of state-of-the-art of parallel and distributed computing in Spring of 1999 (which must have been the time-frame when the book went to final stages of production). However, this also means, that the material presented in the book comes form earlier times. We have thus in our hands a book that is like a Polaroid picture; it presents a high quality snapshot of the state of the art in parallel and distributed computing in late 1990s. This also seemed to be one of the biggest potential weaknesses of handbook-type books. While there are areas of science, where publication of the handbook would seem natural (e.g. handbook of mathematical functions, or a handbook of combinatorial formulas), publication of a handbook for the area that changes as rapidly as parallel and distributed computing could seem a bit strange. The argument would be as follows. What good is a book that gives us snapshot of computing in 1999, while in 2001 the computational reality is substantially different. I had a chance to meet one of the Editors and I asked him about this very issue. The answer was rather unexpected. I was told, that this and other Handbooks are in demand and sell very well. For instance, they had to print more copies of the Handbook under review. After some discussion we came to the conclusion, that readers are hungry for solid work summarizing and bringing together the state-of-the-art in (sub-) disciplines of computer science. And maybe this is also a more general message. We are living in a very fragmented world of computing and we are being constantly attacked by enormous amounts of information delivered in form of journal articles and conference proceedings. This barrage causes an informational overdrive and results in a need for overviews and summaries to provide researchers with a more unified picture of the field(s). No doubts about this the Handbook under review clearly does a great job to satisfy this need. Still, there are few issues that can be raised. They should be viewed suggestions for an improvement of future editions of this Handbook, or as an advice for other future Handbooks. While it is obvious that different authors have a different approach to the discipline it would be very nice if in the Handbook they would be required to have a more unified approach to the material (imposed by the Handbook Editors). For instance, some of the authors concentrate their attention on practical/pragmatic aspect of their sub-area, while others devote most of their time to discuss theoretical foundations of the area and pay almost no attention to the computational practice. Second, the selection of application areas could have been a bit more interesting. High performance computing in molecular sciences in many ways belongs to area of parallel and distributed scientific computing. At the same time there are no examples of database-oriented applications. Obviously, it is not easy to find authors that would tailor chapters to the need of a book (rather than to represent in the chapter their own biases and research interests), but if this was possible for most of the chapters in the first part, then it should have also been possible for the application-related chapters. Overall, the book impresses me. I am not sure if I would pay the requested price, but for anyone interested in a summary of the state-of-the-art of parallel and distributed computing in 1999, this book is definitely a keeper. I would also like to suggest that each library in a research-oriented institution should have a copy of this book. Marcin Paprzycki Oklahoma State University, Tulsa

Recently, distributed computing infrastructures such as grid computing, have witnessed huge developments which have a very important impact on computationally intensive scientific, industrial and engineering problems. Collaborative computing, resources access and sharing facilitated by grid computing systems amplifies concerns about cyber attacks and misbehaviors of grid resources (resources provider). In many cases, an organization may send out jobs for remote execution on untrustworthy machines. Since resource sharing and cooperation among different administrative domains are among the central goals of grid computing, it is necessary to guarantee that, among the shared resources, there are no malicious resources interested in invalidating or corrupting the job results. In order to guarantee reliable jobs execution in grid systems, we have developed a new approach for malicious grid resources tolerance using reputation to improve the efficiency of majority voting mechanisms. The grid broker service investigates the trustworthiness of the grid resources used in the voting procedure; this investigation is based on distributed and hierarchical reputation management system which maintains a reputation value for each grid resource based on its historical behavior. The validation of the result is then decided based on the grid resources reputation level.

Trust is essential in human interaction and this naturally reflects within computer science context, in particular inside internet-based communities. In this work we present an approach based on social networks, which revealed several useful properties, as the small world effect, that can be usefully exploited in addressing the question of trust. We aim at reproducing the behaviour individuals adopt in their life when they establish and maintain trust relationships, sending queries to collect reputations in order to estimate how much trust in new acquaintances. We also consider issues as query forwarding and lifecycle of trusting relationships, aiming at building an effective and efficient model for trust management.

Stephen J. Hartley Oxford University Press, New York, 1998, 260 pp. ISBN 0-19-511315-2, $45.00 Concurrent Programming is a thorough treatment of Java multi-threaded programming for both a stand-alone and distributed environment. Designed mostly for students in concurrent or parallel programming classes, the text is also an excellent reference for the practicing professional developing multi-threaded programs or applets. Hartley first provides a complete explanation of the features of Java necessary to write concurrent programs, including topics such as exception handling, interfaces, and packages. He then gives the reader a solid background to write multi-threaded programs and also presents the problems introduced when writing concurrent programs—namely race conditions, mutual exclusion, and deadlock. Hartley also provides several software solutions that do not require the use of common process and thread mechanisms. Once the groundwork is laid for writing concurrent programs, Hartley then takes a different approach than most Java references. Rather than presenting how Java handles mutual exclusion with the synchronized keyword (although it is covered later), he first looks at semaphore-based solutions to classic concurrent problems such as bounded-buffer, readers-writers, and the dining philosophers. Hartley also uses the same approach to develop Java classes for monitors and message passing. This unique approach to introducing concurrency allows the readers to both understand how Java threads are synchronized and how the basic synchronization mechanism can be used to construct more abstract tools such as semaphores. If there is a shortcoming with the text it is with the lack of sufficient coverage of remote method invocation (RMI), although there is a section covering RMI. This is quite understandable as RMI is a fairly recent phenomenon with the Java community. Also, the classes that Hartley provides could easily implement RMI rather than sockets to handle communication. The strengths of the book include its ease in reading, several examples at the end of chapters, a package similar to Xtango that provides algorithm animation, and a supportive web site by the author (see www.mcs.drexel.edu/~shartley/ConcProgJava/index.html ) including compressed source code. As Java becomes more dominant on the server side of multi-tier applications, writing thread-safe concurrent applications becomes even more important. Concurrent Programming is a strong step towards teaching students and professionals such skills. Greg Gagne, Westminster College of Salt Lake City Salt Lake City, Utah

This special issue is based on a collection of selected papers presented at the Fifth International Conference on Advanced Computing held in Chennai (Madras), India in December 97. The International Conference on Advanced Computing is organized annually in India by the Advanced Computing Society (ACS) which is a premier professional society set up in India to cater to the broad interests in the area of Advanced Computing. One of the significant activities of the Society is to organize regular Meetings/Conferences/Symposia. The Conferences are held annually in India during December. Out of the shortlisted papers presented at the Conference held in Chennai (Madras) during December 97, the following six papers were finally selected after a second round of detailed review of the papers. The first paper On designing and implementing collaborative system using Java-RMI by Rajeev R. Raje, Snehasis Mukhopadhyay, Michael Boyles and Nila Patel describe the use of Java-RMI in designing a collaborative information classifier. The principles of RMI, the details of the prototype, and some preliminary results are presented. The paper primarily concentrates on web-based computing paradigms. In the second paper A framework for performance-based program partitioning , Ram Subramanian and Santosh Pande present an efficient and accurate performance model based program-partitioning approach for parallel architectures. The interactions between computation and communication are captured through behavioral edges . The approach yields significant performance improvement. The third paper DDSCHED: a distributed dynamic real-time scheduling algorithm by Anup K. Bhattacharjee, K. Ravindranath, R. Mall and A. Pal presents a dynamic soft real-time scheduling algorithm for distributed systems. The algorithm is based on a local scheduler and a distributed scheduling scheme. The algorithm takes care of the network delays assuming that the communication protocol is CSMA/CD. In the fourth paper Generic operational decomposition for concurrent systems semantics and reflection , Annie Marcoux, Christine Maurel, Frederic Migeon and Patrick Salle discuss about the reflection in concurrent languages, particularly in actor-based languages. The main objective of the paper is to extend concurrent systems to reflection. The authors present a modular and dynamic description of entity operational management, and extend the decomposition to obtain reflective entities. The fifth paper Parallel programming using visual patterns by A. S. M. Sajeev proposes a two level approach to parallel programming within the context of a visual environment. The first level is the specification of patterns encapsulating process communation and synchronization, and the second level is the use of patterns for parallel programming. The approach encourages reuse of patterns. In the sixth paper An application framework for dynamic distributed software architectures , G. R. Ribeiro-Justo and P. R. F. Cunha present an object-oriented application framework for developing evolving (reconfigurable) software architectures for distributed systems. The application framework is called C++CL. Such a requirement is encountered in banking, industrial control and telecommunications applications. We are extremely thankful to the following reviewers who have helped us in reviewing the papers submitted for this special issue: Lawrence Jenkins N. Mohan Ram Nishit Narang Rajeev Shorey Sameer Adhikari K. Balaji K. Rajan Sumit Kasera Subhrajyothi Bhar Pankaj Sethi Ravindranath Kokku Guest Editors: L. M. Patnaik, Ravi Mittal and K. M. Mehta

In this article we present a novel approach to analyzing performance properties of parallel applications based on event traces. We define a framework for formally specifying compound events that characterize performance behavior. The framework allows the creation of abstract building blocks that represent concepts of the underlying programming model and therefore provide an easy means to specify complex compound events. We show that using these specifications it is possible to automatically locate inefficiencies in parallel applications by looking for occurrences of the corresponding compound events in event traces. We demonstrate how our ideas apply to both the Message Passing Interface (MPI) programming model and to the Open specifications for Multi Processing (OpenMP).

High performance scientific applications are currently implemented using native languages for optimizing performance and utilization of resources. It often deals with thousands of code lines in FORTRAN or in C built of legacy applications. On the other hand new technologies can be exploited to improve flexibility and portability of services on heterogeneous and distributed platforms. We propose here an approach that allows programmers to extend their applications to exploit this kind of services for management purposes. It can be done simply by adding some methods to the original code, which specialize application management on occurrence of particular events. We mean that applications do not need to be rewritten into different languages or adopting specific programming models. We implemented a native console that is used by Mobile Agents to control the application life-cycle. Agents implement a mobile service that supports check-pointing, suspension, resume, cloning and migration of managed applications. A WSRF interface has been provided to Grid users who do not need to be aware about agents technology. We used a FORTRAN code for simulation of plasma turbolence as a real case study.

As the use of wirelessly connected embedded mobile devices grows in vast quantity, their situative use and context sensitive behavior becomes an essential feature. For the implementation of context awareness in mobile appliances, the need for the efficient gathering, representation and delivery of context information evolves. This paper describes issues related to context sensing, representation and delivery, and proposes a new approach for context based mobile computing: Time and event triggered context sensing for mobile devices and an abstract (application and platform independent) representation of context information is introduced. The paper presents showcases of time and event triggered context sensing in wireless environments.

Loosely-coupled Grid environments, based only on Globus services, allow a straightforward resource sharing, as the resources are accessed by using de facto standard protocols and interfaces, while providing non trivial levels of quality of service. This paper describes the execution of a Bioinformatics application over a highly distributed and heterogeneous testbed. This testbed is composed of resources devoted to EGEE and IRISGrid projects and has been integrated by taking advantage of the modular, decentralized and end-to-end architecture of the Grid W ay framework. Results obtained from the experiments have been analyzed using a performance model for high throughput computing applications.