Software Architecture Metrics

Chapter 3. Evolutionary Architecture: Guiding Architecture with Testability and Deployability

Dave Farley

Software architecture is both important and ephemeral. It can determine important characteristics of systems, such as their scalability, performance, and resilience, for example. It is ephemeral in that it is often vague and subjective in how we judge these qualities.

Architectural descriptions and documents best function like tourist maps for the systems we, as architects, build. They allow us to navigate the space without being too precise or specific about the details—which are likely to change. Learning more about our users’ and customers’ needs and demands can change our view of where on the scale the architectural properties of our systems need to sit.

If you work with software architecture, you might be wondering: if I start out with a simple system, how do I cope when demand grows rapidly? What if demand doesn’t grow? How do I deal with growing demands for performance, security, and extensive uptime? How do I maintain my system as a habitable space that evolves easily to meet new or unforeseen demands? How can I keep the doors open to unanticipated change, yet avoid hampering the development process with overelaborate future-proofing?

This chapter makes the case that the answer is a defensive approach: software architects need to design and learn techniques to manage the complexity of the systems they create.

The Importance of Learning and Discovery

Complex systems ...