Production systems are established methods for encoding knowledge in expert systems. It has been pointed out the lack of supporting too1s for developing knowledge-base to use production systems more widely. Especially, there has been a demand for a verification system for production systems. In this report, we present our verification system for OPS5-based production systems. It consists of three steps to verify the knowledge-base. (1) Detect errors automatically. (2) Suggest a correction of errors to user. (3) Correct the errors if user permitted. Our system introduces new concepts called "variable expand" and "expected WME" for detecting more errors than other verification systems. By using "variable expand", we can restrict variable range. And using "expected WME", we can detect some errors that required dynamic information, only using static information from knowledge-base.
