The paper describes a development of a diagnosing and operating system in which mutual cooperation between a system and an operator can be effectively used in decision making. Firstly, a concept of cooperation between the system and the operator was proposed. The authors discuss the cooperative method for plant operation and diagnosis. Then, the authors designed a framework of this system which is composed of three modules, namely a diagnosing module, an interface module and a supporting tool module. In this system, a knowledge base is represented by utilizing a fault tree and describing additional information for coopera-tive decision making. The authors implemented a prototype of the system for diagnosing human errors and malfunctions in a bio-process system. Finally, the availability of the prototype system is shown through simulated system operation.
