"The Problem of Asking the Minimum Number of Questions in Horn Clause Systems"

Mathematical and Computer Modeling, 1994, Vol. 20, No. 9, pp. 75-87.

Evangelos Triantaphyllou and Jinchang Wang

This paper deals with the issue of question asking strategies in expert systems with Horn clause rule bases. A good strategy would ask as few questions as possible to reach a conclusion. This paper describes the development of an efficient and effective heuristic approach which is an extension of the strategy developed by Wang and Vande Vate [16]. Similar to the original strategy, the proposed approach is also organized into two phases. In the first phase a set of candidate questions is formed as in the original strategy. In the second phase a question is selected from the previous set. A new question selection rule is used in the proposed strategy. This rule is optimal, given set of candidate questions. Furthermore, computational results indicate that the new question asking strategy is a highly effective and efficient practical approach.

Key Words:
Question asking strategies, Horn clauses, inference engine, backward chaining, expert systems, set cover problem, heuristic approaches.

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