In this paper, the authors use the concepts of a 'virtual process'and a 'real process', and use a 'constraint blackboard' for CAPP for non-axisymmetric hot-forging products. A virtual process is a primitive and basic forming process, which may exist only in the mind of a process designer. A real process is a complex process havig virtual processes as its elements. When the designer designs a forging process, he guesses the transitional pre-form shape in each successive virtual process, and finally assembles the virtual processes into one real process. These virtual processes restrict each other in compressing direction or parting line, deformability, and ability of combination and works cooperatively when they are assembled. The authors researched such virtual processes and their constraints, entered them as 'processing cases data' into a database called the 'processing case base', and implemented an expert system for connecting rod products. A 'constraint blackboard' is a common working memory which can be accessed by the procedures described in every processing case. The system starts design from the final shape and works back toward the raw material. It establishes a manufacturing plan at each virtual process. Once a virtual process starts to be designed, some procedures on the processing case are executed and new constraint is written on the constraint blackboard. When the other virtual process is designed, the system examines the process by referring to the constraint blackboard. Thus, the design process of each virtual process is done cooperatively to others. The system continues to assemble virtual processes into one real process until it fails to find a virtual process which is consistent with past fixed virtual processes.