The modularization of process plants is an approach to cope with the changing requirements of the process industry, such as highly volatile markets and shorter product lifecycles. Each module offers services as encapsulated process functions to the superior control system for the orchestration. These services are controlled in a state-based way. The encapsulation of these services in a reasonable way is a difficult task, because aspects of process and automation engineering must be considered. This contribution introduces an approach for the encapsulation of process functions in services from an automation point of view. Furthermore, the operation modes of modules, services and field devices are discussed. Additionally, possible solutions for the orchestration based on recipe models are introduced. The developed concepts have been tested within a simulation environment.