Mere data sharing between engineering design systems and manufacturing systems does not represent an ideal integrated system. While data sharing represents an important aspect of an integrated design and manufacturing environment, an equally critical aspect is the interaction capability of the two systems. This interaction could be in the form of feedback and request messages between the design and manufacturing systems. The goal of this study is to investigate the issues involved in the development of a conceptual message model that will facilitate an upstream and a downstream communication between the design activities and process planning activities. The development of a message model is an attempt to capture the design/process planner dialogue in a computer representable and interpretable form.