DCE: A guide to developing portable applications [Book Reviews]

years these members have written about their research's technical details and its problem domain or context. Consequently , Birman and Van Renesse were able to select from a rich body of work. The book has 2 1 chapters, which are divided into four sections. The " Fundamentals " section introduces the problems Isis is intended to deal with and the Isis approach's general nature. This section defines and discusses at length the virtual synchrony programming model of distributed systems. Two chapters deal with controversies. One argues RPC's inadequacy as a, tool for constructing reliable distributed systems; the other defends the utility of causally ordered group communication. (Readers interested in the honorable opposition's side of the second controversy should read " Understanding the Limitations of Causally and Totally Ordered Communication, " by David Cheriton and Dale Skeen, in the 1991 Proceedings of the Symposium on Operating Systems Principles, ACM Press.) " Redesign, " the second section, describes the motivation, design, and new research initiatives of Horus. When the book was being written, Horus was very much a work in progress. Nevertheless , this section's chapters capture the spirit of Horus's design, the direction of the ongoing research, and many of the lessons learned during the development of the original Isis Toolkit. The " Protocol " section contains chapters detailing the key group-communication and fault-detection protocols on which Isis and Horus are built. These are among the most technically challenging chapters. Readers who are " notation averse " might be inclined to skip Chapters 12,13, and 14. I would encourage those who are interested in more than a superficial understanding of how the system works to persevere. As is often the case when dealing with problems associated with distributed consensus, the Isis protocols are not unduly complex, but are in some ways quite subtle. These chapters present the material carefully and, for the most part, straightforwardly. The final section, " Tools and Applications , " describes a fairly broad range of applications that have been built with Isis. Meta is a toolht for constructing distributed reactive systems, which include process-control systems. T h e Paralex programming environment is intended to simplify designing and building parallel, distributed programs. The M I S query and reporting system was built for the World Bank's Planning and Budgeting Department. Distributed M L provides distributed computing extensions to standard M L (metalanguage) programming language. Each chapter explains …