Taking advantage of IoT, services and Cloud technologies, the development of Cloud of Things (CoT) changes the way control application are engineered and developed moving from a dedicated design and development of control applications to a Control as a Service vision. This vision requires developing a new architecture to connect physical and logical objects as well as integrating basic control patterns to organize a consistent control service orchestration. To fit this challenge, we propose a multi-layer Control as a Service architecture to describe control systems in a holistic way. The integration of a context manager, analysing continuously the system environment as well as the control system behaviour is used to monitor and orchestrate on the fly the deployment of context-aware control services. Thanks to this context dependent orchestrator, adaptive control system can be implemented.