Software Architecture in Practice, 4th Edition

The software development community is coming to grips with the fact that roughly 80 percent of a typical software system’s total cost occurs after initial deployment. Most systems that people work on are in this phase. Many programmers and software designers never get to work on new development—they work under the constraints of the existing archit... See more

• If your system requires high performance, then you need to pay attention to managing the time-based behavior of elements, their use of shared resources, and the frequency and volume of their interelement communication.


• If modifiability is important, then you need to pay attention to assigning responsibilities to elements and limiting the interaction

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Architecture represents a common abstraction of a system that most, if not all, of the system’s stakeholders can use as a basis for creating mutual understanding, negotiating, forming consensus, and communicating with each other. The architecture—or at least parts of it—are sufficiently abstract that most nontechnical people can understand it to th... See more

This practice gained attention in the early 2000s through the ideas of Alistair Cockburn and his notion of a “walking skeleton.” More recently, it has been adopted by those employing MVP (minimum viable product) as a strategy for risk reduction.

The fidelity of the system increases as extensions are added, or early versions are replaced by more complete versions of these parts of the software. In some cases, the parts may be low-fidelity versions or prototypes of the final functionality; in other cases, they may be surrogates that consume and produce data at the appropriate rates but do li... See more

Every architecture, no matter what it is, partitions possible changes into three categories: local, nonlocal, and architectural.

• A local change can be accomplished by modifying a single element—for example, adding a new business rule to a pricing logic module.


• A nonlocal change requires multiple element modifications but leaves the underlying archite

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If you want your implementation to conform to an architecture, then it must conform to the design decisions prescribed by the architecture. It must have the set of elements prescribed by the architecture, these elements must interact with each other in the fashion prescribed by the architecture, and each element must fulfill its responsibility to t... See more

Software architecture is a manifestation of the earliest design decisions about a system, and these early bindings carry enormous weight with respect to the system’s remaining development, its deployment, and its maintenance life. It is also the earliest point at which these important design decisions affecting the system can be scrutinized.

Decisions at all stages of the life cycle—from architectural design to coding and implementation and testing—affect system quality. Therefore, quality is not completely a function of an architectural design. But that’s where it starts.