Responding to User Queries in a Collaborative Environment

We propose a plan-based approach for responding to user queries in a collaborative environment. We argue that in such an environment, the system should not accept the user's query automatically, but should consider it a proposal open for negotiation. In this paper we concentrate on cases in which the system and user disagree, and discuss how this disagreement can be detected, negotiated, and how final modifications should be made to the existing plan. 1 I n t r o d u c t i o n In task-oriented consultation dialogues, the user and expert jointly construct a plan for achieving the user's goal. In such an environment, it is important that the agents agree on the domain plan being constructed and on the problem-solving actions being taken to develop it. This suggests that the participants communicate their disagreements when they arise lest the agents work on developing different plans. We are extending the dialogue understanding system in [6] to include a system that responds to the user's utterances in a collaborative manner. Each utterance by a participant constitutes a proposal intended to affect the agents' shared plan. One component of our architecture, the evaluator, examines the user's proposal and decides whether to accept or reject it. Since the user has knowledge about his/her particular circumstances and preferences that influence the domain plan and how it is constructed, the evaluator must be a reactive planner that interacts with the user to obtain information used in building the evaluation meta-plan. Depending on the evaluation, the system can accept or reject the proposal, or suggest what it considers to be a better alternative, leading to an embedded negotiation subdialogue. In addition to the evaluator, our architecture consists of a goal selector, an intentional planner, and a discourse realizer. The goal selector, based on the result of the evaluation and the current dialogue model, selects an appropriate intentional goal for the system to pursue. The intentional planner builds a plan to achieve the intentional goal, and the discourse realizer generates utterances to convey information based on the intentional plan. This paper describes the evaluator, concentrating on cases in which the system and user disagree. We show how the system determines that the user's proposed additions are erroneous and, instead of directly responding to the user's utterances, conveys the disagreement. Thus, our work contributes to an overall dialogue system by 1) extending the model in [6] to eliminate the assumption that the system will automatically answer the user's questions or follow the user's proposals, and 2) capturing the notion *This material is based upon work supported by the National Science Foundation under Grant No. IRI-9122026. of cooperative responses within an overall collaborative framework that allows for negotiation. 2 T h e T r i p a r t i t e M o d e l Lambert and Carberry proposed a plan-based tripartite model of expert/novice consultation dialogue which includes a domain level, a problem-solving level, and a discourse level [6]. The domain level represents the system's beliefs about the user's plan for achieving some goal in the application domain. The problem-solving level encodes the system's beliefs about how both agents are going about constructing the domain plan. The discourse level represents the system's beliefs about both agents' communicative actions. Lambert developed a plan recognition algorithm that uses contextual knowledge, world knowledge, linguistic clues, and a library of generic recipes for actions to analyze utterances and construct a dialogue model[6]. Lambert's system automatically adds to the dialogue model all actions inferred from an utterance. However, we argue that in a collaborative environment, the system should only accept the proposed additions if the system believes that they are appropriate. Hence, we separate the dialogue model into an existing dialogue model and a proposed model, where the former constitutes the shared plan agreed upon by both agents, and the latter the newly proposed actions that have not yet been confirmed. Suppose earlier dialogue suggests that the user has the goal of getting a Master's degree in CS (GetMasters(U, CS)). Figure 1 illustrates the dialogue model that would be built after the following utterances by Lambert's plan recognition algorithm modified to accommodate the separation of the existing and proposed dialogue models, and augmented with a relaxation algorithm to recognize ill-formed plans[2]. U: I want to satisfy my seminar course requirement. Who's teaching CS689? 3 T h e E v a l u a t o r A collaborative system should only incorporate proposed actions into an existing plan if they are considered appropriate. This decision is made by the evaluator, which will be discussed in this section. This paper only considers cases in which the user's proposal contains an infeasible action (one that cannot be performed) or would result in an ill-formed plan (one whose actions do not contribute to one another as intended)[9]. We argue that the evaluator, in order to check for erroneous plans/goals, only needs to examine actions in the proposed model, since actions in the existing model would have been checked when they were proposed. When a chain of actions is proposed, the evaluator starts examining from the top-most action so that the most general action that is inappropriate will be addressed.