AN INSTRUCTABLE PRODUCTION SYSTEM: BASIC DESIGN ISSUES11This Paper Draws Ideas From An Ongoing Project Involving C. Forgy, J. McDermott, Kamesh Ramakrishna, And P. Langley, In Addition To The Authors. Forgy And McDermott Have Been Responsible For The Implementation Of The OPS Production System Architecture And Other System Facilities Described Here. We Acknowledge The Joint Role These People Have Played In Developing The Ideas In This Paper, But They Are Not Responsible For Our Detailed Expression Or Interpretation Of Them. This Research Was Supported In Part By The Defense Advanced Research Projects Agency Under Contract No. F44620-73-C-0074 And Monitored By The Air Force Office Of Scientific Research.