A methodology for the rapid prototyping of process control systems which is based on an original extension to classical Petri nets is presented. The proposed nets, called PROT nets, provide a suitable framework to support the following activities: building an operational specification model; evaluation, simulation, and validation of the model; and automatic translation into program structures. PROT nets are shown to be translatable into Ada program structures concerning concurrent processes and their synchronizations. The authors illustrate this translation in detail using, as a working example, the problem of tool handling in a flexible manufacturing system.