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.