A framework of a knowledge-based expert operation planning system, TURNPLAN, is described. The system incorporates a feature-based part representation scheme to smooth the essential information flow from design intent to manufacturing practice. Its main functions initially consist of the determination of machining sequence, cutting parameters and cutting tools. To make this system a complete working module for full integration of CAD/CAM, its knowledge base has been further upgraded so that determination of work-holding methods, and generation of tool paths and the associated NC part programs, are included in the system. This integrated system is developed on a PC-based computer using PROLOG, which is found suitable in a batch-type job shop environment for industrial applications. A practical example is included to highlight certain features of the system and the paper concludes with implications for further research.