A new OOA model and methodology are proposed in this paper. n e proposed OOA model is composed of an object model, which specipes objects and the relationships between them, and a function model, which specipes system functions and their operation logic. The proposed OOA methodology develops the specipcations of objects and system functions in parallel by following a functional refinement process. Since system functions are speciped clearly in the OOA model, the user can easily understand what the system can do by tracing its spec@cation. The object model and function model are developed in parallel, so the consistency between system functions and objects are kept throughout the OOA process.16 0-8186-&480-6/94 $03.00 8 1994 IEEE