Insights into the Dialogue Processing of VERBMOBIL

Insights into the Dialogue Processing of VERBMOBIL Jan Alexandersson Norbert l:{,eithinger Elisabeth Maier DFKI GmbH Stuhlsatzenhausweg 3 D-66123 Saarbriicken, Germany {alexanders s on, re ithinger ,maier}@dfki. un-sb, de Abstract We present the dialogue module of the speech-to-speech translation system VERB- MOBIL. We follow the approach that the solution to dialogue processing in a medi- ating scenario can not depend on a single constrained processing tool, but on a com- bination of several simple, efficient, and ro- bust components. We show how our solu- tion to dialogue processing works when ap- plied to real data, and give some examples where our module contributes to the cor- rect translation from German to English. 1 Introduction The imPlemented research prototype of the speech- to-speech translation system VEaBMOBIL (Wahlster, 1993; Bub and Schwinn, 1996) consists of more than 40 modules for both speech and linguistic processing. The central storage for dialogue information within the overall system is the dialogue module that ex- changes data with 15 of the other modules. Basic notions within VERBMOBIL are tu~8 and utterances. A turn is defined as one contribution of a dialogue participant. Each turn divides into utter- ances that sometimes resemble clauses as defined in a traditional grammar. However, since we deal ex- clusively with spoken, unconstrained contributions, utterances are sometimes just pieces of linguistic ma- terial. For the dialogue module, the most important di- alogue related information extracted for each utter- ance is the so called dialogue act (Jekat et al., 1995). Some dialogue acts describe solely the illocutionary force, while other more domain specific ones describe additionally aspects of the propositional content of an utterance. Prior to the selection of the dialogue acts, we ana- lyzed dialogues from VERBMOBIL'S corpus of spoken and transliterated scheduling dialogues. More than 500 of them have been annotated with dialogue re- lated information and serve as the empirical founda- tion of our work. Throughout this paper we will refer to the exam- ple dialogue partly shown in figure 1. The transla- tions are as the deep processing line of VERBMOBIL provides them. We also annotated the utterances with the dialogue acts as determined by the semantic evaluation module. ' '//' ' shows where utterance boundaries were determined. We start with a brief introduction to dialogue pro- cessing in the VERBMOBIL setting. Section 3 intro- duces the basic data structures followed by two sec- tions describing some of the tasks which are carried out within the dialogue module. Before the con- cluding remarks in section 8, we discuss aspects of robustness and compare our approach to other sys- tems. 2 Introduction to Dialogue Processing in VERBMOBIL In contrast to many other NL-systems, the VEaB- MOBIL system is mediating a dialogue between two persons. No restrictions are put on the locutors, ex- cept for the limitation to stick to the approx. 2500 words VERBMOBIL recognizes. Therefore, VERBMO- BIL and especially its dialogue component has to fol- low the dialogue in any direction. In addition, the dialogue module is faced with incomplete …

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