Information systems science is advancing in many directions with rapid strides. Many diversified ideas, methodologies, and techniques have been conceived and developed for improving the design of information systems and for inventing new methods for solving complex information problems. This volume, the seventh of a continuing series on information systems science, covers five timely topics which are in the mainstream of current interest in this growing field. In each chapter, an attempt is made to famil iarize the reader with some basic background information on the advances discussed, so that this volume may be used independently or in conjunction with the previous volumes. The emphasis in this volume is centered upon diagnosis for digital systems, distributed information networks, micro computer technology, and data structures for pattern recognition. In recent years, digital systems have found widespread applications in on-line real-time processing. Such applications demand high reliability, availability, and serviceability. Reliability may be improved through the use of highly reliable parts. Improvement in integrity may be accompanied by retry operation and redundant configuration. Serviceability may be improved by making use of fault diagnosis techniques. Chapter 1 is devoted to this important subject. Fault diagnosis techniques are developed to improve serviceability and to shorten mean time for repair. Kitamura, Tashiro, and Inagaki discuss many recent methods for fault diagnosis and explain them with illustrative examples.