Collaborating on Referring Expressions

Collaborating on Referring Expressions Peter A. Heeman Department of Computer Science University of Toronto Toronto, Canada, M5S 1A4 heeman@ai.toronto.edu Abstract This paper presents a computational model of how conversational participants collaborate in making re- ferring expressions. The model is based on the plan- ning paradigm. It employs plans for constructing and recognizing referring expressions and meta-plans for constructing and recognizing clarifications. This al- lows the model to account for the generation and un- derstanding both of referring expressions and of their clarifications in a uniform framework using a single knowledge base. I, Introduction In the dialogue below 1, person A wants to refer to some object and have person B identify it. Person A does this by uttering a referring expression; however, A's expression fails to allow B to uniquely identify the object. Person B then tries to clarify A's referring expression by expanding it. A rejects B's clarification and replaces it, which al- lows B to identify the referent of the refashioned referring expression. A: 1 See the weird creature B: 2 In the corner? A: 3 No, on the television B: 4 Okay. This paper presents a computation model of Clark and Wilkes-Gibbs's work on how conversational partici- pants collaborate in forming referring expressions [2]. Our model takes the role of one of the participants, either the participant who initiates the referring expression, the ini- tiator, or the one who is trying to identify the referent, the responder. It accounts for how the initiator constructs the initial referring expressions and how she and the responder then collaborate in clarifying the referring expression until it is acceptable. Each step of the collaboration consists of a clarification of the referring expression and a subsequent understanding of the clarification. This work is based on the planning paradigm. The knowledge that is needed to choose the content of a refer- ring expression is encoded in plans. This allows an agent to use the same knowledge base for both constructing and recognizing initial referring expressions. Furthermore, the I This example is a simplified version of [6] S.2.4a (1-8). knowledge needed to clarify a referring expression is en- coded as plans. These are meta-plans that take an instan- tiated plan corresponding to a referring expression as a parameter. The meta-plans reason about the failed con- straints or effects of the instantiated plan in order to clarify it. These repairs can subsequently be understood by per- forming plan recognition. This approach allows the entire collaborative process to be expressed in a uniform frame- work with a single knowledge base. II. Referring as Action Plans encode a relationship between goals and the prim- itive actions that will accomplish these goals. Hence, a set of primitive actions is needed that is relevant in the domain of referring expressions [1]. We use the primitive actions s-refer and s-attr. S-refer is performed by the initiator to signal to the responder that she is referring to an object, and that she intends him to identify the object. S-attr ascribes some …

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