2.3 Why Is Architectural Design So Important?
There is a very high cost to a project of not making certain design decisions, or of not making them early enough. This manifests itself in many different ways. Early on, an initial architecture is critical for project proposals (or, as it is sometimes called in the consulting world, the pre-sales process). Without doing some architectural thinking and some early design work, you cannot confidently predict project cost, schedule, and quality. Even at this early stage, an architecture will determine the key approaches for achieving architectural drivers, the gross work-breakdown structure, and the choices of tools, skills, and technologies needed to realize the system.
In addition, architecture is a key enabler of agility, as we will discuss in Chapter 9. Whether your organization has embraced Agile processes or not, it is difficult to imagine anyone who would willingly choose an architecture that is brittle and hard to change or extend or tune—and yet it happens all the time. This so-called technical debt occurs for a variety of reasons, but paramount among these is the combination of a focus on features—typically driven by stakeholder demands—and the inability of architects and project managers to measure the return on investment of good architectural practices. Features provide immediate benefit. Architectural improvement provides immediate costs and long-term benefits. Put this way, why would anyone ever “invest” in architecture? The answer is simple: Without architecture, the benefits that the system is supposed to bring will be far harder to realize.
Simply put, if you do not make some key architectural decisions early and if you allow your architecture to degrade, you will be unable to maintain sprint velocity, because you cannot easily respond to change requests. However, we vehemently disagree with what the original creators of the Agile Manifesto claimed: “The best architectures, requirements, and designs emerge from self-organizing teams”. Indeed, our demurral with this point is precisely why we have written this book. Good architectural design is difficult (and still rare), and it does not just “emerge”. This opinion mirrors a growing consensus within the Agile community. More and more, we see techniques such as “disciplined agility at scale”, the “walking skeleton”, and the “scaled Agile framework” embraced by Agile thought leaders and practitioners alike. Each of these techniques advocates some architectural thinking and design prior to much, if any, development. To reiterate, architecture enables agility, and not the other way around.
Furthermore, the architecture will influence, but not determine, other decisions that are not in and of themselves design decisions. These decisions do not influence the achievement of quality attributes directly, but they may still need to be made by the architect. For example, such decisions may include selection of tools; structuring the development environment; supporting releases, deployment, and operations; and making work assignments.
Finally, a well-designed, properly communicated architecture is key to achieving agreements that will guide the team. The most important kinds to make are agreements on interfaces and on shared resources. Agreeing on interfaces early is important for component-based development, and critically important for distributed development. These decisions will be made sooner or later. If you don’t make the decisions early, the system will be much more difficult to integrate. In Section 3.6, we will discuss how to define interfaces as part of architectural design—both the external interfaces to other systems and the internal interfaces that mediate your element interactions.