An Introduction to Interactive Discourse Processing from the Perspective of Plan Recognition and Text Planning

People engage in task-oriented dialogues to carry out or plan a task. Each participant in such an interaction must be capable of processing plans in two ways. First, each participant must be capable of understanding the plans that the other participant is using. Researchers have developed theories and models about how computational systems should go about recognizing the plans and goals of another participant, both at the subject-matter level and at the level of the communication. This area of research is called plan recognition. Secondly, each participant must be able to make their owns plans to communicate. This area of natural language research is called text planning. Interactive systems -- systems that understand natural language and that can produce natural language to engage in a task-related interaction -- must address the issue of how understanding plans (the process of plan recognition) relates to making plans for the interaction (the process of text planning). We provide an introduction to these two research areas in natural language processing. Those who need to be familiar with both areas -- to conduct research at their intersection -- will find this introduction useful for building systems that both understand what people are trying to do when they speak and that can actively participate in the interaction.