Planning Text about Plans Interactively ∗

In expository discourse, listeners ask questions in response to unsatisfactory explanations. A system that explains interactively must be able to recognize how to elaborate its answer to produce an explanation that meets a listener’s informational needs. Sometimes, listeners ask questions that digress from the purpose of the discussion. Therefore, a system that provides interactive explanations must also be able to distinguish pertinent questions from questions that digress from the discussion purpose. It must also be able to recognize questions that are incoherent. This paper discusses the representation issues that are involved in building such a system. The Interactive Discourse Planner (IDP) plans text to describe and/or justify a domain plan interactively. To perform these tasks, both the system’s text plans and the domain plans are represented uniformly. The uniform representation of information makes it possible for IDP to access both domain and discourse information to recognize how to plan each response. The system’s planning rules refer to information at both the domainand discourse-level. Therefore, these levels of information are reasoned about together to plan additional discourse. IDP uses questions from the user to recognize how to extend its own text plan in a way that both satisfies its listener and achieves the system’s discourse goal. In the process of trying to recognize ways to expand its own text plan, IDP can detect three types of digressions from the discourse purpose that the user can initiate with a question. Two types of text plan representations that are used in the system make it possible for the system to distinguish these types of digressions. As a testbed, IDP plans text to discuss driving route plans.