. . . and they all lived happily ever after . . .
In this chapter we step back from the details of the warehouse management process control system to take a bird's-eye view of the pattern story that guided the creation of its architecture. We discuss how this story reinforces the properties of pattern languages, and how the pattern language for distributed computing from Part III of this book supported the selection of the specific pattern sequence that underlies the story.
Looking back at the pattern story about the architecture of the warehouse management process control system may give the impression that the selection and application of its constituent patterns was fairly obvious: perhaps just common sense, or even predetermined. The story has a natural, intuitive flow and we can easily follow its plot. It may therefore appear that creating this architecture was straightforward.
This impression, however, is simplistic and misleading, missing many of the subtleties that make the act of design anything but a handle-turning process, regardless of patterns. Analyzing the pattern sequence reveals that it was thoughtfully chosen rather than randomly picked. Most obviously, its individual patterns address the specific requirements of the warehouse management process control system—definitely a prerequisite for creating a well-defined software architecture. But just selecting the right patterns is by no means sufficient to achieve an effective ...