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Evolving self-adaptive services using planning-based reflective middleware

Self-adaptive systems often use a middleware-based approach where adaptation mechanisms and policies are separated and externalized from the application code. Such separation facilitates the independent analysis of application and adaptation. In the QuA middle-ware, we use mirror-based reflection and service planning to support the development and execution of self-adaptive systems. A mirror provides meta information about a service's behavior and implementation throughout all life-cycle phases, including its performance in different contexts. Service planning supports dynamic discovery, utility-based and context-aware evaluation, and selection of alternative implementations of a given service.Here we argue that the QuA middleware is also able to support certain forms of evolution of adaptive systems. Since in QuA new implementation alternatives or updated versions of software are automatically discovered and considered during service planning, evolution both during run time and load time is supported. Experimental results from evolving a state-of-the-art adaptive media streaming application using our middleware are also presented.