Structuring Coherent Explanation: The Use of Diagnostic Strategies in an Expert Critiquing System

摘要

Diagnostic strategies were used internally by INTERNIST to direct its questioning based on how well it could separate competing diagnoses. The present paper explores how a critiquing expert system can use similar diagnostic strategies in order to coherently structure its prose output. Four such strategies have been implemented in ICON, an expert system that critiques radiologic diagnosis. The strategies used by ICON are named PURSUE, RULE-IN-RULE-OUT, CONFLICT and NOT-ENOUGH-INFORMATION. After analyzing each case on the basis of its rule-based knowledge, ICON chooses one of the above strategies. This strategy then influences both the choice of the comments used to construct the critique as well as its overall structure and tone. Thus, ICON adapts the form of its critique to its content, producing natural, readable prose that enables one to clearly percieve how far the system has resolved competing diagnoses.