Spoken Variable Initiative Dialog: An Adaptable Interface

Recent advances in speech recognition technology have raised hopes about the development of practical spoken natural language interfaces. Embedding the speech recognition technology within a sophisticated dialog processing mechanism can overcome many of the traditional problems in spoken natural language systems. This paper presents a theory of natural language dialog that enables: (1) robust behavior in the presence of word misrecognitions; (2) exible behavior according to the level of user expertise; and (3) practical implementation of spoken natural language systems using commercial hardware. In addition to the theory, the paper also describes experimental results obtained from using an implementation of this theory. Major advances in recent years in speech recognition technology (see 7] and 13]) 1 have raised expectations about the development of practical spoken natural language interfaces. Such interfaces can provide user exibility as well as allow users to have their hands and eyes busy on the task at hand. Examples of such situations include equipment repair, telephone assistance, airline piloting, automobile driving, heavy equipment operation, etc. Traditionally, voice natural language systems have not been able to provide the required performance due to a lack of exibility, a lack of eeective goal-seeking behavior, and poor speech recognition rates, to name a few reasons. These problems can be circumvented by embedding the speech recognition technology within a dialog processing mechanism with the following capabilities: uses problem solving to help the human user carry out the task; conducts subdialogs to carry out the various subgoals needed to complete the task, switching between subdialogs as needed; exploits knowledge about the user to determine what information is known and what information needs to be communicated; exploits context dependent expectations about user responses to assist in interpreting the user's responses; and engages in dialog where the task initiative can vary from strongly computer controlled to strongly user controlled or somewhere in between. This ability to vary the level of initiative is called variable initiative dialog, and it represents a major advance in the utility of natural language systems. With such a capability, a natural language system can 1 In addition, several projects demonstrating dramatically improved speech recognition performance were presented at the 1993 ARPA (Advanced Research Projects Agency) Human Language Technology Workshop.