Visibility of Control in Adaptive Systems

<p>Adaptive systems respond to changes in their internal state or external environment with guidance from an underlying control system. ULS systems are particularly likely to re- quire dynamic adaptation because of their decentralized con- trol and the large number of independent stakeholders whose actions are integral to the system's behavior. Adaptation may take various forms, but the system structure will al- most inevitably include one or more closed feedback loops. We argue that adaptability is a characteristic of a solution, not of a problem, and that the feedback loop governing con- trol of adaptability should be explicit in design and analysis and either explicit or clearly traceable in implementation.</p>