A Computational Model of Collaboration on Reference in Direction-Giving Dialogues

In a conversation, a speaker sometimes has to refer to an object that is not previously known to the hearer. This type of reference occurs frequently in dialogues where the speaker is giving directions to a particular place. To make a reference, the speaker attempts to build a description of the object that will allow the hearer to identify it when she later reaches it. This thesis presents a computational model of how an agent collaborates on reference in direction-giving dialogues. Viewing language as goal-oriented behaviour, we encode route descriptions, referring expressions, and discourse actions in the planning paradigm. This allows an agent to construct plans that achieve communicative goals by means of surface speech actions, and to infer plans and goals from these actions. The basis is that a referring expression plan is acceptable to an agent if she is con dent that the plan is adequate as an executable identi cation plan. By considering the salience of the features used in a referring expression plan, an agent can evaluate her con dence in its adequacy. Driven by the implicit intention of making plans mutually acceptable, the conversants collaborate until the hearer is con dent in the adequacy of the current referring expression plan. In doing so, the conversants use suggestion and elaboration discourse actions that operate on the current plan. While collaborating, an agent is in a mental state that includes the intention to achieve the goal of having the direction recipient understand the directions, the plan the agents are currently considering, and a focus of attention into the plan. This collaborative state governs the discourse by sanctioning both the adoption of goals, and the mutual acceptance of plans. Re ecting the inherent symmetry in collaborative dialogue, the model can act as both speaker and hearer, and can play the roles of both the direction-giver and the recipient.