On Knowing What to Say: Planning Speech Acts

The goal of this thesis is to model some of the cognitive structures and processes involve d in how people decide what to say in purposeful conversation. The main concern is to show how a speaker's knowledge of his/her hearer influences what s/he says. Utterances in such dialogues, where speakers can be presumed to be speaking for reasons, can best be viewed as the performance of "speech acts" (e.g., requesting). By modeling the process of deciding what to say as one of problem-solving, we show that the same mechanisms used to plan non-linguistic actions are applicable to planning of speech acts. The methodology of this research employs a computer program that integrates beliefs, goals, problem-solving, and reasoning, with the use of language. The program does this by planning speech acts when it determines that to achieve its situational goals, it needs to influence someone else's behavior. The system is able to plan request speech actrions to influence its user's goals, and inform speech acts to influence his/her beliefs. In addition, it is shown that speech acts can be used to achieve subgoals of other such acts. For instance, in addition to requesting that the user perform some action, the system can also decide to supply him/her with information necessary to performing that action -- information that it believes s/he does not already have. Our model is extendable to the more general problem of planning multiparty speech acts -- ones where actions requested by the speaker involve acts to be performed by parties other than the hearer. [MORE].