This paper describes an expert system to assist process development. T
his system, PRINCE, aims to specify the parameters of a refining unit
while respecting the constraints on the operating conditions and produ
cts. The originality of the procedure lies in the juxtaposition and co
operation of different types of knowledge, i.e. production rules conta
ining expertise as well as equations; the use of numerical procedural
codes for simulation. An overall task architecture manages the concati
nation and communication among all these types of knowledge.