Part Two: Quality Attributes

In Part II, we provide the technical foundations for you to design or analyze an architecture to achieve particular quality attributes. We do not discuss design or analysis processes here; we cover those topics in Part III. It is impossible, however, to understand how to improve the performance of a design, for example, without understanding something about performance.

In Chapter 4 we describe how to specify a quality attribute requirement and motivate design techniques called tactics to enable you to achieve a particular quality attribute requirement. We also enumerate seven categories of design decisions. These are categories of decisions that are universally important, and so we provide material to help an architect focus on these decisions. In Chapter 4, we describe these categories, and in each of the following chapters devoted to a particular quality attribute—Chapters 5–11—we use those categories to develop a checklist that tells you how to focus your attention on the important aspects associated with that quality attribute. Many of the items in our checklists may seem obvious, but the purpose of a checklist is to help ensure the completeness of your design and analysis process.

In addition to providing a treatment of seven specific quality attributes (availability, interoperability, modifiability, performance, security, testability, and usability), we also describe how you can generate the material provided in Chapters 5–11 for other quality attributes that we have not covered.

Architectural patterns provide known solutions to a number of common problems in design. In Chapter 13, we present some of the most important patterns and discuss the relationship between patterns and tactics.

Being able to analyze a design for a particular quality attribute is a key skill that you as an architect will need to acquire. In Chapter 14, we discuss modeling techniques for some of the quality attributes.