The theme that weaves through this book is that architectures do not exist by themselves, but are part of a cycle. Architecture is a means toward an end. It is influenced by the functional and quality goals of both the customer and the developing organization. It is also influenced by the architect's background and experiences and by the technical environment. Architecture in turn influences the system being developed, and it may be a core asset that influences the developing organization. The system also has an effect on the developing organization; the architecture; and, potentially, the technical environment. This effect affects the future goals for the system and its organization. The influences and feedback loops that surround an architecture form the ABC.
An architecture is a description of system structures, of which there are several (module decomposition, process, deployment, layered, etc.). Architecture is the first artifact that can be analyzed to determine how well its quality attributes are being achieved, and it also serves as the project blueprint. An architecture serves as the vehicle for communication, is the manifestation of the earliest design decisions, and is a re-usable abstraction that can be transferred to new systems. These are the things we mean when we use the word architecture.
The A-7E Avionics System was a project that paid special attention to the engineering and specification of three distinct architectural structures to achieve developmental simplicity and modifiability. The chapter shows how (and why) the structures were designed and documented.