A computer model of conversation

This paper is addressed to the problem of how it is possible to conduct coherent, purposeful conversations. It describes a computer model of a conversation between two robots, each robot being represented by a section of program. The conversation is conducted in a small subset of English, and is a mixed-initiative dialogue which can involve interruptions and the nesting of one segment of dialogue in another. The conversation is meant to arise naturally from a well defined setting, so that it is clear whether or not the robots are saying appropriate things. They are placed in a simple world of a few objects, and co-operate in order to achieve a practical goal in this world. Their conversation arises out of this common aim; they have to agree on a plan, exchange information, discuss the consequences of their actions, and so on. In previous language-using programs, the conversation has been conducted by a robot and a human operator, rather than by two robots. In these systems, it is almost always the human operator who takes the initiative and determines the overall structure of the dialogue, and the processes by which he does so are hidden away in his mind. The aim of our program is to make these processes totally explicit, and it is for this reason that we have used two robots and avoided human participation. Thus the main focus of interest is not the structuring of individual utterances, but the higher-level organisation of the dialogue, and how the dialogue is related to the private thoughts which underlie it. The program has two kinds of procedure, which we call ROUTINES and GAMES, the Games being used to conduct sections of conversation and the Routines to conduct the underlying thoughts. These procedures can call each other in the normal way. Thus the occurrence of a section of dialogue will be caused by the call of a Game by a Routine; and when the section of dialogue ends, the Game will exit, returning control to the Routine which called it. There are several Games, each corresponding to a common conversational pattern, such as a question and its answer, or a plan suggestion and the response to it. The Games determine what can be said, who will say it, how each remark will be analysed, and how it will be responded to. They are thus joint procedures, in which the instructions are divided up between the robots. When a section of dialogue occurs, the relevant Game will be loaded in the minds of both robots, but they will have adopted different roles in the Game, and will consequently perform different instructions and make different utterances.