This paper discusses how dialog expectations may be exploited in solving some important problems of dialog processing. Our model for expectation-driven dialog processing extends the theoretical model of attentional state by Grosz and Sidner as it provides a practical application of the model. In addition to a presentation of our model and a discussion of its application to dialog processing problems, the paper reports on results obtained from the use of our voice-interactive dialog system. The results are baaed on over 140 dialogs and over 2800 spoken user utterances.Among researchers in natural language processing it is common knowledge that contextual information must be used in order to properly understand and respond to utterances in a dialog (see Allen [5] for a general discussion). This is true for all types of dialogs including tack-oriented dialogs, the object of study in our research. Consider the following subdialog (C denotes the computer, and U the user. )(1) c:You need to measure the voltage between cormectora 24 and 83. (2) u:Uhere do I connect this red wire? (3) c:To connector 24.(4) u: Where is it?(5) c: To the right of the switch.(6) U:
I have made the connection.In utterance(2) theuser refers to "this red wire" although no wire has been explicitly mentioned. Itcame into context when the discussion of meaeuring the voltage was introduced. This implicitly introduced the voltmeter into context along with its wires, one of which is this red wire. Sinrilarly, the "it" of utterance (4)refers to connector 24, which is mentioned in utterance (3). User utterances (2) and (4) cannot be understood in isolation.They can only be understood by using the contextual information available as the result of previous utterances in the dialog.Permission to copy without fee all or part of this material is grantsd provided that the oopiss ars not made or distributed for direot commercial advantage, ths ACM copyright notice and the titls of the publication and its date appear, and notioe is given that copying ia by parmiasion of the Association for Computing Machinery.To oopy otherwise, or to republish, requirss a fee andtor specific permission. e 1992 AcM 0.88791-502.X/92/0002/01 23...$1.50This paper discusse8 how a particular feature of dialogs, eqectation, may be exploited in providing a solution to problems of dialog interpretation.Specifically, we discuss how expectation may be exploited in handling the following important problems:1. Understanding ill-formed inputs.
Using context for proper interpretation of utter-ances.
Participating in variable initiative dialogs.
A variable initiative dialog is a dialog where either dialog participant can have control at different points in the dialog. A variable initiative dialog system contrasts with other N L dialog systems such as [6], [7], [8], [15], [19], [21], [27], and [29], for which the dialog is either purely user controlled or purely computer controlled.Our research has focused on taak-oriented dialogs, dialogs held in conjunction with the performance of some task ...