This book focuses on the practice of designing objects as integral members of a community where each object has specific roles and responsibilities. The authors present the latest practices and techniques of Responsibility-Driven Design and show how students can apply them as they develop modern object-based applications. Working within this conceptual framework, Rebecca Wirfs-Brock and Alan McKean present how user requirements, system architecture, and design patterns all contribute to the design of an effective object model. They introduce a rich vocabulary that students can use to discuss aspects of their designs, discuss design trade-offs, and offer practical guidelines for enhancing the reliability and flexibility of applications. In addition, case studies and real-world examples demonstrate how the principles and techniques of Responsibility-Driven Design apply to real-world software designs.