We are now poised to understand the synthesis of form and function known as architecture. Form, a system attribute consisting of elements and structure, was developed in Chapter 4. Function, a system attribute consisting of entities of function and interactions through operands, collectively forming the functional architecture, was discussed in Chapter 5. Now we will explore system architecture, the combination of form and function.

Up to this point, we have agreed that system architecture is an abstract description of the entities of a system and the relationships between those entities. We will now adopt the more descriptive definition given in Box 6.1. The definition includes five key terms. Function, form, relationship, and context were discussed in Chapters 2 through 5. Concept is a mental image, notion, or system vision that maps form and function; it will be discussed in Chapter 7.

As Figure 6.1 suggests, architecture is not an independent attribute, but the mapping between form and function.

The importance of architecture is expressed in the Principle of Value and Architecture (Box 6.2). In essence, if we are to deliver value with the system we build, it must have good architecture. Section 6.2 takes on the central question of how form and function map to each other. Section 6.3 discusses three additional ideas: what form appears in architecture to deal with non-idealities along the value pathway; what functions and forms must be present to support the value pathway; and the form and function of interfaces. Section 6.4 discusses the implications of operational behavior on system architecture. Finally, in Section 6.5, we survey the ways in which architecture can be represented. In this chapter, we will be guided by the ­questions in Table 6.1.