Learning Run-time Compositions of Interacting Adaptations

Self-adaptive systems continuously adapt to internal and external changes in their execution environment. In context-based self-adaptation, adaptations take place in response to the characteristics of the execution environment, captured as a context. However, in large-scale adaptive systems operating in dynamic environments, multiple contexts are often active at the same time, requiring simultaneous execution of multiple adaptations. Complex interactions between such adaptations might not have been foreseen or accounted for at design time. For example, adaptations can partially overlap, requiring only partial execution of each, or they can be conflicting, requiring some of the adaptations not to be executed at all, in order to preserve system execution. To ensure a correct composition of adaptations, we propose ComInA, a novel reinforcement learning based approach, which autonomously learns interactions between adaptations as well as the most appropriate adaptation composition for each combination of active contexts, as they arise. We present an initial evaluation of ComInA in an urban public transport network simulation, where multiple adaptations to buses, routes, and stations are required. Early results show that ComInA correctly identifies whether adaptations are compatible or conflicting and learns to execute adaptations which maximize system performance. However, further investigation is needed into how best to utilize such identified relationships to optimize a wider range of metrics and utilize more complex composition strategies.