Building Evolutionary Architectures, 2nd Edition

Chapter 5. Evolutionary Architecture Topologies

Discussions about architecture frequently boil down to coupling: how the pieces of the architecture connect and rely on one another. Many architects decry coupling as a necessary evil, but it’s difficult to build complex software without relying on (and coupling with) other components. Evolutionary architecture focuses on appropriate coupling—​how to identify which dimensions of the architecture should be coupled to provide maximum benefit with minimal overhead and cost.

In this chapter, readers will garner a deeper understanding of architecture coupling, how that affects architectural structure, and how to evaluate the structure of software architectures to more effectively evolve them. We also provide some concrete terminology and advice on architecture topology from the component up through the system level.

Evolvable Architecture Structure

Different architecture styles have different evolution characteristics, but there is nothing inherent in the style that controls its ability to evolve. Rather, it boils down to the coupling characteristics supported by the architecture. It turns out that at least two different efforts from the past have identified the key enabler of evolution in software. Each of them provides a valuable perspective on coupling in architecture.

Connascence

In 1996, Meilir Page-Jones published What Every Programmer Should Know About Object-Oriented Design (Dorset House), which is a duplex book: one part ...