Completeness and Consistency in a Rule-Based System

The builders of a knowledge-based expert system must ensure that the system will give its users accurate advice or correct solutions to their problems. The process of verifying that a system is accurate and reliable has two distinct components: checking that the knowledge base is correct, and verifying that the program can interpret and apply this information correctly. The first of these components has been the focus of the research described in this chapter; the second is discussed in Part Ten (Chapters 30 and 31). Knowledge base debug, ng, the process of checking that a knowledge base is correct and complete, is one component of the larger problem of knowledge acquisition. This process involves testing and refining the system's knowledge in order to discover and correct a variety of errors that can arise during the process of transferring expertise from a human expert to a computer system. In this chapter, we discuss some common problems in knowledge acquisition and debugging and describe an automated assistant for checking the completeness and consistency of the knowledge base in the ONCOCIN system (discussed in Chapters 32 and 35).