Abstract
We present a dialogue control method called the “dual-cost method”, by which a spoken dialogue system conveys information relevant to a user request by a concise dialogue within the confines of the system's knowledge stored in its database. Due to speech recognition errors, a system has to carry out a “confirmation dialogue” to clarify the user request. A confirmation dialogue should be concise since a lengthy one destroys the flow of the overall dialogue. There are cases where the user request is beyond the system's knowledge since a user does not know what knowledge the system has. In such cases, conventional methods have a problem of invoking unnecessary confirmations since they attempt to confirm the whole contents of the request. To resolve this problem, we introduce the notions of confirmation cost and information transfer cost. The confirmation cost is the length of a confirmation dialogue and depends on the speech recognition rate. The information transfer cost is the length of a system response and depends on the system's knowledge. The dual-cost method controls a dialogue based on the minimization of these two costs and can avoid unnecessary exchanges, which are inevitable in conventional methods.
