Decisions, Models, and Monitoring -- A Lifecycle Model for the Evolution of Service-Based Systems

The process of engineering and provisioning service-based systems (SBS) follows a complex and dynamic lifecycle with different phases and levels of abstraction. We tackle the problem of making this lifecycle explicit, providing development time and runtime support for evolutionary changes in such systems. SBSs are modeled as integrated ecosystems consisting of four conceptual layers (or phases): design, implementation, deployment, and runtime. Our work is driven by the notion that identifying the right changes (monitoring) and effecting of these changes (adaptation) usually takes place individually on each layer. While considering changes on a single layer (e.g., runtime adaptation) is often sufficient, some cases require systematic escalation to adjacent layers. We present a generic lifecycle model that provides an abstracted view of the problem domain and can be mapped to concrete artifacts on each individual layer. We introduce a real-life scenario taken from the telecommunications domain, which serves as the basis for discussion of the challenges and our solution. Based on the scenario and our experience from a research project on Virtual Service Platforms, we evaluate three concrete use cases which illustrate the diversity of evolutionary changes supported by the approach.