Different Spoken Language Dialogues for Different Tasks A Task-Oriented Dialogue Theory

Spoken language dialogue is a comfortable form of communication between humans and computers, which is present in a growing number of commercial systems. For each task which can be comfortably performed in spoken language dialogue with the computer, there is an equivalence class of tasks which can be performed using similar dialogue management technology. Each such task class has a number of minimum functional requirements which, once they have been met by the technology, will enable comfortable spoken language humancomputer dialogue. The paper presents these requirements in terms of dialogue elements such as initiative, system feedback, predictions and system focus, dialogue history, user models and meta-communication. Three increasingly complex task class/dialogue type pairs are distinguished and their corresponding minimum dialogue elements are presented and illustrated from our own development of spoken language dialogue systems. The result is a first version of task-oriented dialogue theory which may support the design and specification of increasingly sophisticated spoken language dialogue systems.