This paper presents PROTOB, an object oriented language and methodology based on PROT nets, and the CASE environment that supports it. PROT nets integrate extended dataflows and Petri nets into an object oriented formalism. The CASE environment consists of several tools supporting specification, modelling and prototyping activities using the PROTOB language within the framework of the operational software life cycle paradigm. As its major application area it addresses distributed systems, such as real-time embedded systems, communication protocols and manufacturing control systems. The CASE environment automatically generates the distributed and object oriented implementation code in Ada or C providing advanced features such as multitasking and system distribution over a LAN. A model of a Flexible Manufacturing System and its production control software are analysed as a case study.