97 Things Every Software Architect Should Know

Chapter 24. Use Uncertainty As a Driver

Kevlin Henney is an independent consultant and trainer. His work focuses on patterns and architecture, programming techniques and languages, and development process and practice. He is coauthor of A Pattern Language for Distributed Computing and On Patterns and Pattern Languages (both from Wiley).

—Kevlin Henney

CONFRONTED WITH TWO OPTIONS, most people think that the most important thing to do is to make a choice between them. In design (software or otherwise), it is not. The presence of two options is an indicator that you need to consider uncertainty in the design. Use the uncertainty as a driver to determine where you can defer commitment to details and where you can partition and abstract to reduce the significance of design decisions. If you hardwire the first thing that comes to mind, you're more likely to be stuck with it, so that incidental decisions become significant and the softness of the software is reduced.

One of the simplest and most constructive definitions of architecture comes from Grady Booch: "All architecture is design but not all design is architecture. Architecture represents the significant design decisions that shape a system, where significant is measured by cost of change." What follows from this is that an effective architecture is one that generally reduces the significance of design decisions. An ineffective architecture ...