The theory of graceful extensibility: basic rules that govern adaptive systems

The paper introduces the theory of graceful extensibility which expresses fundamental characteristics of the adaptive universe that constrain the search for sustained adaptability. The theory explains the contrast between successful and unsuccessful cases of sustained adaptability for systems that serve human purposes. Sustained adaptability refers to the ability to continue to adapt to changing environments, stakeholders, demands, contexts, and constraints (in effect, to adapt how the system in question adapts). The key new concept at the heart of the theory is graceful extensibility. Graceful extensibility is the opposite of brittleness, where brittleness is a sudden collapse or failure when events push the system up to and beyond its boundaries for handling changing disturbances and variations. As the opposite of brittleness, graceful extensibility is the ability of a system to extend its capacity to adapt when surprise events challenge its boundaries. The theory is presented in the form of a set of 10 proto-theorems derived from just two assumptions—in the adaptive universe, resources are always finite and change continues. The theory contains three subsets of fundamentals: managing the risk of saturation, networks of adaptive units, and outmaneuvering constraints. The theory attempts to provide a formal base and common language that characterizes how complex systems sustain and fail to sustain adaptability as demands change.