This paper presents automatic methods for the segmentation and classication of dialog acts (DA). In Verbmobil it is often sucient to recognize the sequence of DAs occurring during a dialog between the two partners. Since a turn can consist of one or more successive D As we conduct the classication of DAs in a two step procedure: First each turn has to be segmented into units which correspond to a DA and second the DA categories have to be identied. For the segmentation we use polygrams and multi{layer perceptrons, using prosodic features. The classication of DAs is done with semantic classication trees and polygrams.

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In this paper, we show how prosodic information can be used in automatic dialogue systems and give some examples of promising new approaches. Most of these examples are taken from our own work in the VERBMOBIL speech-to-speech translation system and the EVAR train timetable dialogue system. In a 'prosodic orbit', we first present units, phenomena, annotations and statistical methods from the signal (acoustics) to the dialogue understanding phase. We show then, how prosody can be used together with other knowledge sources for the task of resegmentation and how an integrated approach leads to better results than a sequential use of the different knowledge sources; then we present a hybrid approach which is used to perform a shallow parsing and which uses prosody to guide the parsing; finally, we show how a critical system evaluation can help to improve the overall performance of automatic dialogue systems.

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