Dialogue management in spoken dialogue systems with Degrees of Grounding

Spoken dialogue systems - computers that interact with humans through spoken conversations - must become more robust before they will be widely accepted. One tradition in improving error-handling in spoken dialogue systems involves studying and implementing grounding behavior as used by humans. When humans converse, they typically work together to establish mutual understanding by using behavior such as repetitions ("you said seven o'clock...,") acknowledgments ("ok, got it,") and repairs ("No, I said ten o'clock.") These types of evidence of understanding combine to help humans establish that the material under discussion is mutually understood to a level sufficient for the current purposes. However, previous work in grounding has not examined how to explicitly represent the degree to which material is grounded during a dialogue, whether this can be useful for dialogue management in spoken dialogue systems, and what advantages this brings to implemented systems.;This thesis presents the novel Degrees of Grounding model. This model answers open questions by using a corpus study to identify how to explicitly represent the degree to which material has reached mutual understanding during a dialogue. The model describes how evidence of understanding combines to define the degree of groundedness of some material under discussion, how grounding criteria can be defined in terms of those degrees of groundedness, and how algorithms working with these concepts can be used for dialogue management.;The components of the Degrees of Grounding model were developed by analyzing behavior of artillery fire request dialogues in a virtual training environment. An evaluation confirmed that the dialogue management algorithms agreed with human judgments, and that the dialogue manager was capable of managing dialogues in the virtual environment while providing more detailed descriptions of dialogue behavior than were previously available. The Degrees of Grounding model was then implemented in a virtual human for tactical questioning training, and a set of experiments with users showed that the Degrees of Grounding model produced more appropriate grounding utterances when compared to baseline systems.