Residuality Theory¶

Residuality Theory, developed by Barry O'Reilly, applies ideas from complexity science to software architecture by treating a system as a collection of interacting elements under stress. Architects subject the system to hypothetical stressor events and observe what structure survives across multiple scenarios: these persistent elements are called "residuals" and represent the true structural core of the architecture. The theory frames architecture not as a blueprint to be preserved but as a set of stable attractors, giving teams a principled way to distinguish what must be designed with care from what can be treated as volatile or disposable.

See also: Software Architecture · Wardley Mapping