Chapter 2. The Beast

Il m'a dit qu'il ne faut jamais / Vendre la peau de l'ours qu'on ne l'ait mis par terre. (He told me never to sell the bear's skin before one has killed the beast.)

”Jean de La Fontaine, Fables , "L'Ours et les deux Compagnons" V. 20

The remainder of this book is built around a modernization case study, affectionately nicknamed "The Beast." This case study combines elements from numerous modernization efforts we have participated in. The need to do so is straightforward: Large modernization efforts often take many years . By the time the final system is deployed, the methods and techniques used in the requirements phase have likely faded into obscurity. This case study is referenced throughout the remainder of this book to explain our approach to legacy system modernization.

The Beast involves the modernization of a large supply-chain system that we refer to as the Retail Supply System (RSS). Written primarily in COBOL, RSS has evolved over 30 years. When asked if anyone understood the design of this system, one of the lead engineers quipped, "Yes, but they are all dead now." As a result of this unstructured evolution, the system has become extremely brittle and difficult to maintain. RSS operates at more than 90 sites. Although the application is the same, the data stored is specific to each location. Because of the size and complexity of the system, a big-bang replacement was infeasible. The system is being modernized in a series of efforts, each of which replaces and retains significant portions of the legacy system.

Working with a large, complex system has presented the development team with many challenges, not the least of which is the information infrastructure of the enterprise. This infrastructure consists of a patchwork of mainframe, minicomputer, and desktop applications ”both centralized and distributed ”under dispersed control. These systems are separated by geography and variations in policies, cultures, and customs among various groups in the organization. Additionally, many of these systems are being modernized at the same time. Therefore, the composition of enterprise systems interfacing with the modernized RSS is schedule driven and time dependent. For example, if the RSS replacement system is deployed in 3 years, it will need to be integrated with the legacy financial system. However, if it slips 1 year, the RSS must be integrated with the replacement financial system unless the schedule for that system has slipped as well. Needless to say, this has created a rather dynamic planning environment. Despite these problems, all these legacy systems are critical and cannot be discarded without their capabilities being provided elsewhere.

The principal goal of the development effort was to create a modernized system that could be supported and easily maintained . The RSS management felt that this could be best achieved by developing a modern architecture based on software components that could be easily deployed at various geographical locations yet maintain the ability to communicate with the remainder of the system. These large-grained software components , or business objects, should also support industry-standard interfaces. This allows the use of commercial products ”if not now, then as they become available.

Additionally, the modernized system was required to comply with the organization's proprietary Standard Retail Framework (SRF). The SRF is based on existing industry standards from the Open Applications Group , Sun Microsystems, and other industry groups. This constraint required that business objects be implemented by smaller-grained components, such as Enterprise JavaBeans (EJB), Java servlets, and CORBA servers. These small-grained components are conceptually closer to the components definition provided by Szyperski in his book on component software [Szyperski 98]. The process of creating a modern architecture along these lines is referred to as componentization. Although it is more appropriate to refer to this as business objectification, this phrase is too cumbersome.