In this paper we describe an architecture of a new integrative process planning system as a part of computer integrated manufacturing research system. The process planning procedure is comprised of three phases: feature completion, process selection and process sequencing. We applied a knowledge-based approach to feature completion and process selection, and the space search algorithm for process sequencing. Description of these phases is provided and underlying knowledge representation explained. Integration between the process planning, on the one side, and CAD and scheduling, on the other, is discussed. System implementation has been described and several examples of the system execution are shown.