Planning Dialogue Contributions With New Information

The paper discusses a framework for planning contributions in a spoken dialogue system, and focuses especially on the three/'s: Incrementality, Immediacy, and Interactivity. The emphasis is on communicative principles and the notion of NewInfo, or the information focus of the utterance. NewInfo provides a natural way of to conceptualize the planning process and to generate utterances on the level of granularity •required in spoken interaction. 1. I N T R O D U C T I O N The question that we will investigate is the starting point of generation, and we argue that this is NewInfo, the piece of new information exchanged in interaction, with which the mutual context gets updated. This may sound like sliding on the '!slippery slope" of (McDonald, 1993), who points out that the answer to the question 'how far back does generation go?' is tied to the proportional amounts of linguistic and contextual information in the specification which serves as the source of generation. However, we would like to stress the separation of communicative knowledge from the minimal information units used as the basis for generation, and that the selection of the information units and the way they axe actually communicated are subject to conditions which may require changes in one of the tasks before the other one is properly completed. In (spoken) interaction, utterances consist of fine-grained information units to which the listener immediately reacts by giving feedback or a response, and this feedback then directs the speaker to modify her utterance accordingly. Hence, we might as well slide the slippery slope all the way down, and conclude that generation starts simultaneously with interpretation, as a reaction to the presented information. The initial 'messag e' is then gradually specified into a linguistic expression with respect to languagespecific knowledge and communicative • requirements of the situation. Consequently, in this paper we focus on the three rs in generation: Incrementality, Immediacy, and Interactivity. The research is still ongoing, so we pose questions more than provide answers. After introducing the three I's, the specific questions we will discuss are: (1) What are suitable utterance• units for exchanging information in spoken dialogues? (2) What is the relationship between NewInfo and organisation of the task/d0main information? (3) What kind of requirements are imposed on the generator? 1 aThroughout the paper we use generator to refer to the whole system that generates rather than analyses natural language. The component of the generation system that mostly deals with world-knowledge, tasks, plans and communicative goals, is called planner, while realiser is the component which concerns lexico-semantic and syntact ic information. Sentence planning is also called micro-planning.