Tight coupling of speech recognition and dialog management - dialog-context dependent grammar weighting for speech recognition

In this paper we present our current work on a tight coupling of a speech recognizer with a dialog manager and our results by restricting the search space of our grammar based speech recognizer through the information given by the dialog manager. As a result of the tight coupling the same lingustic knowledge sources can be used in both, speech recognizer and dialog manager. Furthermore, the flexible context-free grammar implementation of our speech decoder Ibis allows weighting of specific rules at run-time to restrict the search space of the recognizer for the next decoding step. These rules are given by the dialog manager depending on the current dialog context. With this approach we were able to reduce the word error rate of user responses to system questions by 3.3% relative for close talking and 16.0% relative, when using distant speech input. The sentence error rates were reduced by 2.2%, 9.2% respectively.