A natural-language interface to a constraint satisfaction system

Many modelling problems, such as the construction of project plans, can be considered as the construction of a term in a language, under constraints. The activities involved in such term-construction, such as expanding an activity into sub-activities may rather naturally be given a hierarchical structure; such structures in their turn may induce a structured task-oriented dialogue. The authors describe the way in which such construction, viewed as a cooperative problem solving activity, gives rise to a dialogue between the (two) participants. A system is described which uses internal task and term models to drive a mixed-initiative dialogue. At each point in the dialogue, the system generates a virtual tree of natural language sentences which constitute responses the user is able to make, including the giving of information, requests to the system for further information or opportunities for the user to move the focus of discourse. The virtual tree is displayed on a high-resolution screen as initial phrases: the user may explore the tree structure to construct sentences by movement of the mouse, using the technology of `walking menus´. A transcript of the dialogue, and a graphical model of the current state of the constructed model are also displayed on the screen