AQUA: Questions that Drive the Explanation Process
In the doctoral dissertation from which this chapter is drawn, Ashwin Ram presented an alternative perspective on the processes of story understanding, explanation, and learning. The issues that Ram explores in that dissertation are similar to those that are explored by the other authors in this book, but the angle that Ram takes on these issues is somewhat different. Ram's exploration of these processes is organized around the central theme of question asking. For Ram, understanding a story means identifying questions that the story raises, and questions that it answers. Question asking also serves as a lens through which each of the sub-processes of is viewed: the retrieval of stored explanations, for instance, is driven by a library of what Ram calls "XP retrieval questions"; likewise, evaluation is driven by another set of questions, called "hypothesis verification questions". The AQUA program, which is Ram's implementation of this question-based theory of understanding, is a very complex system, probably the most complex among the programs described in this book. AQUA covers a great deal of ground; it implements the entire case-based explanation process in a question-based manner. In this chapter, we have focused on the high-level description of the questions the programs asks, especially the questions it asks when constructing and evaluating explanations of volitional actions.