Modernizing Legacy Systems - Software Technologies, Engineering Processes, and Business Practices

From the Book: Software systems become legacy systems when they begin to resist modification and evolution. However, the knowledge embodied in legacy systems constitutes significant corporate assets. Assuming these system still provide significant business value, they must then be modernized or replaced. This book describes a risk-managed approach to legacy system modernization that applies a knowledge of software technologies and an understanding of engineering processes within a business context.Audience Modernizing Legacy Systems: Software Technologies, Engineering Processes and Business Practices should be useful to anyone involved in modernizing a legacy system. As a software engineer, it should help you understand some of the larger business concerns that drive a modernization effort. As a software designer, this book should help you understand the impact of legacy code, coupled with incremental development and deployment practices, on design activities. As a system architect, this book explains the processes and techniques that have failed or succeeded in practice. It should also provide insight into how you can repeat these successes and avoid the failures. As an IT manager, this book explains how technology and business objectives influence the software modernization processes. In particular, it should help you answer the following questions: When and how do I decide if a modernization or replacement effort is justified? How do I develop an understanding of the legacy system? How do I gain an understanding of, and evaluate the applicability of, infsystem technologies that can be used in the modernization of my system? When do I involve the stakeholders and how can I reconcile their conflicting needs? What role does architecture play in legacy system modernization? How can I estimate the cost of a legacy system modernization? How can I evaluate and select a modernization strategy? How can I develop a detailed modernization plan? Organization and Content Modernizing Legacy Systems: Software Technologies, Engineering Processes and Business Practices shows how legacy systems can be incrementally modernized. It uses and extends the methods and techniques described in Building Systems from Commercial Components Wallnau, 2001 to draw upon engineering expertise early in the conceptual phase to ensure realistic and comprehensive planning. This book features an extensive case study involving a major modernization effort. The legacy system in this case study consists of nearly 2 million lines of COBOL code developed over 30 years. The system is being replaced with a modern system based on the Java 2 Enterprise Edition (J2EE) architecture. Additional challenges include a requirement to incrementally develop and deploy the system. We look at the strategy used to modernize the system; the use of Enterprise JavaBeans, message-oriented middleware, Java, and other J2EE technologies to produce the modern system; the supporting software engineering processes and techniques; and the resulting system. Chapters 1 of this book provides an introduction to the challenges and practices of software evolution and Chapter 2 introduces the major case study in the bo introduces the Risk-Managed Modernization (RMM) approach which is elaborated in Chapters 4 through 17 and illustrated by the case study. Throughout Chapters 4 through 17 we provide an activity diagram of RMM as a road map to each chapter. Chapter 18 provides some recommendations to help guide your modernization efforts (although these recommendations cannot be fully appreciated without reading the main body of the book).Throughout this book we use the Unified Modelling Language (UML) to represent architecture drawings and design patterns. A brief introduction to UML is provided in Chapter 6.