  This paper presents a computational model of how conversational participants
collaborate in order to make a referring action successful. The model is based
on the view of language as goal-directed behavior. We propose that the content
of a referring expression can be accounted for by the planning paradigm. Not
only does this approach allow the processes of building referring expressions
and identifying their referents to be captured by plan construction and plan
inference, it also allows us to account for how participants clarify a
referring expression by using meta-actions that reason about and manipulate the
plan derivation that corresponds to the referring expression. To account for
how clarification goals arise and how inferred clarification plans affect the
agent, we propose that the agents are in a certain state of mind, and that this
state includes an intention to achieve the goal of referring and a plan that
the agents are currently considering. It is this mental state that sanctions
the adoption of goals and the acceptance of inferred plans, and so acts as a
link between understanding and generation.
