Establishing the relationship between discourse models and user models

Many current research efforts have focused on building cooperat ive systems that interact with the{r users in a natural language such as English. To be effective, these systems must be robust, their dialog must be coherent, and their responses must be helpful to the user. A user m o d e l (UM), which can be modified during the interaction to represent updated beliefs about the current user, is one mechanism that can contribute to a robust, coherent, and cooperat ive dialog. In general, when we as speakers describe certain situations, we try to communicate these situations to our listeners. As proposed by some researchers (Webber 1978, Kamp 1984), speakers do so by attempting to get their listeners to construct an appropriate model: a d i scourse mode l . A discourse model (DM) is viewed as containing representations of entities, along with their properties and relations they participate in. The key, then, in successful communication is for the speaker to transmit as much information about those entities, their properties and relations to the listener so as to achieve the goals of the current interaction. From the point of view of a system, a computational discourse model is used by the system to generate and/or interpret a discourse. This paper focuses on the relationship between DMs and UMs. It starts by describing what a DM is, and the role it plays in a coherent di~dog. It then describes what a UM is, and the role it plays in a cooperat ive dialog. I argue that the DM should be viewed as one part of the UM-tha t is, as one part of the system's model of the user. The examples of the natural language interactions are presented in the context of a natural language interface to an expert system that provides advice on cooking with chilies. (Part of the data was taken from the section "Cooking with Chilies" that appeared in Bon A p p e t i t magazine, December 1986. The expert system can provide information about the different varieties of chili peppers as well as descriptions of how to " tu rn down the hea t " of the chilies (make them less spicy), and how to cook with them without getting any kind of skin or eye irritations.) I justify this by showing how DMs can be viewed as part of UMs and how both models can affect each other. In other words, part of the UMs that systems have correspond to the DM, that is, a representat ion of what is talked about in a specific interaction. This piece, which changes with each discourse, affects the UM and varies from interaction to interaction.