An architecture is worthless if nobody can understand what it is or how to use it. Documenting an architecture is the crowning step in creating it, freeing the architect from having to answer hundreds of questions about it and serving to capture it for current and future stakeholders.
You must understand the stakeholders of the architecture and how they expect to use the documentation. Treat the task of documenting an architecture as documenting the set of relevant views and then supplementing that with cross-view information. Use the stakeholders to help choose the relevant views.
Box-and-line diagrams, whether rendered in an informal notation or in something like UML, tell only a small part of the story. Augment them with supporting documentation that explains the elements and relationships shown in the primary presentation. Interfaces and behavior are important parts of the architecture picture.
This chapter presented a prescriptive organization for documenting software architectures. You may ask why we have not strictly adhered to it in the architectural case studies in this book. A fundamental principle of technical documentation of any kind, and software architecture documentation in particular, is to write so that the material is of the most use to the anticipated readers. Here, the reader wants an overview of the system, its motivations, and how it meets its quality goals?the reader isn't going to analyze it or build to it. Thus, the descriptions that we provide are less formal and less detailed than what we would recommend for construction or analysis. In that spirit, we use primary presentations (cartoons) to convey general information; however, in lieu of a formal element catalog to fill in the detail, we give a narrative description.