Patterns remain one of the most important new technologies contributing to software engineering, system design, and development. All indications are that patterns will continue to grow in significance for years to come as more and more developers have come to rely on design patterns to help them deliver reusable and cost effective applications in a more timely fashion. This volume is a collection of the current best practices and trends in the patterns community. The patterns contained in this book provide effective, tested, and proven software design solutions for developers in all domains, institutions, and organizations. The third in a series of books documenting patterns for professional software developers, this volume continues the tradition of informational excellence established by the first two volumes. Pattern Languages of Program Design 3 is unique from the previous two volumes in that it includes international submissions, having gathered the best papers from both Plop '96 and EuroPLoP '96. A wide range of pattern-related topics are covered, and the patterns are arranged by topic so software engineers can easily select the patterns of greatest relevance to their needs and application domains. This book goes beyond teaching software engineers that design patterns are powerful tools to impart understanding -- it shows you where and when patterns are best applied.