Strengthening Adaptation in Cyber-Physical Systems via Meta-Adaptation Strategies

The dynamic nature of complex Cyber-Physical Systems puts extra requirements on their functionalities: they not only need to be dependable, but also able to adapt to changing situations in their environment. When developing such systems, however, it is often impossible to explicitly design for all potential situations up front and provide corresponding strategies. Situations that come out of this “envelope of adaptability” can lead to problems that end up by applying an emergency fail-safe strategy to avoid complete system failure. The existing approaches to self-adaptation cannot typically cope with such situations better—while they are adaptive (and can apply learning) in choosing a strategy, they still rely on a pre-defined set of strategies not flexible enough to deal with those situations adequately. To alleviate this problem, we propose the concept of meta-adaptation strategies, which extends the limits of adaptability of a system by constructing new strategies at runtime to reflect the changes in the environment. Though the approach is generally applicable to most approaches to self-adaptation, we demonstrate our approach on IRM-SA—a design method and associated runtime model for self-adaptive distributed systems based on component ensembles. We exemplify the meta-adaptation strategies concept by providing three concrete meta-adaptation strategies and show its feasibility on an emergency coordination case study.