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 01] to draw on 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.

Chapter 1 provides an introduction to the challenges and practices of software evolution. Chapter 2 introduces the major case study in the book. Chapter 3 introduces the risk-managed modernization (RMM) approach, which is elaborated in Chapters 4 through 17 and illustrated by the case study. At the beginning of Chapters 4 through 17, we provide an activity diagram of RMM as a road map to the 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 Modeling Language (UML) to represent architecture drawings and design patterns. A brief introduction to UML is provided in Chapter 6.

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