Computer Integrated Manufacturing is often misconstrued as simply the integration of CAD and CAM. In fact it is much more. It is the systems approach of tying together the various automation tools available today, so as to enable the control of an entire manufacturing operation. This includes the business functions as well. The generally accepted way to go about this is to develop a database management system, with the required capabilities. It is stressed here that Manufacuring Resource Planning - II (MRP-II), has the best inherent features, for the tying together of the various manufacturing functions. Initial work deals with Computer Aided Design (CAD) and MRP-II integration, the integration being centered around parts specifications, product structures, and engineering changes. A model for this integration is presented along with the rules of interaction between the systems. The model is based on an interoperability system, and uses a formal language named 'Update Dependencies' which has been defined for specifying the various operations in and between MRP-II and CAD. This has been used to test the model design specification. Future work includes the introduction of Computer Aided Process Planning (CAPP), to the present model.