Book excerpt: The challenges of designing, building, and maintaining large-scale, distributed enterprise systems are truly daunting. Written by and for IT professionals, IT Architectures and Middleware, Second Edition, will help you rise above the conflicts of new business objectives, new technologies, and vendor wars, allowing you to think clearly and productively about the particular challenges you face. This book focuses on the essential principles and priorities of system design and emphasizes the new requirements emerging from the rise of e-commerce and distributed, integrated systems. It offers a concise overview of middleware technology alternatives and distributed systems. Numerous increasingly complex examples are incorporated throughout, and the book concludes with some short case studies. Topics covered include: Middleware technology review Key principles of distributed systems: resiliency, performance and scalability, security, and systems management Information access requirements and data consistency Application integration design Recasting existing applications as services In this new edition, with updates throughout, coverage has been expanded to include: Service-oriented architecture concepts Web services and .NET technology A more structured approach to system integration design