Architecture provides the foundation from which systems are built, and models are one way to define the vision on which your architecture is based. The scope of architecture can be that of a single application, of a family of applications, for an entire organization, or for an international infrastructure such as the Internet. The focus of this chapter is on architectural modeling for a single system, although much of the advice is pertinent to larger efforts. Regardless of the scope, my experience is that you can take an agile approach to the modeling, development, and evolution of architectures. Table 10.1 overviews the artifacts described in this chapter for architectural modeling.

For our purposes the architecture for a system is simply its high-level design. Good architectures are based on requirements—developers taking on the role of architect will often analyze the pertinent requirements as part of the architectural modeling process. One way to look at architecture is that it, along with analysis, is the bridge between requirements and design. Architects will also consider high-level design decisions such as “What will we build this system from?”, “How will the parts of this system fit together?”, and “How can we ensure this system will work under less-than-perfect (or real-world) conditions?”