Automatic Disambiguation of Discourse Particles

Automatic Disambiguation of Discourse Particles Kerstin Fischer and Hans Brandt-Pook Graduate Program Task-oriented Communication University of Bielefeld, Germany Postfach 100131, D-33501 Bielefeld fischer@nats.informatik.uni-hamburg.de hbrandt@techfak.uni-bielefeld.de Abstract In spite of their important quantitative role, discourse particles have so far been ne- glected in automatic speech processing for two reasons: Firstly it is not clear what they may contribute to the aims of auto- matic speech processing, and secondly their functions seem to vary so much that it seems difficult to identify the information relevant to such aims. The approach pre- sented here therefore attempts to provide au- tomatic means to distinguishing the different readings of discourse particles and to filter- ing out the information which can be use- ful for speech understanding systems, em- ploying positional information and their role within a dialogue model of the respective do- main, two types of information which are es- pecially easy to obtain. First results indicate that discourse particles can indeed be auto- matically disambiguated on the basis of the model proposed. 1 Introduction Discourse particles, as for instance Ger- man ja, nein, ach, oh, and ~hrn, and En- glish well, yes, oh, ah, and uhm (Schiffrin, 1987), are extremely frequent phenomena of spontaneous spoken language dialogues. For instance, in informal German human- to-human communication, their frequency ranges between 8.8% and 9.8% (Fischer and Johanntokrax, 1995). In human-computer interaction, this prominent quantitative role decreases; however, they may still constitute 6.6% of the 150 most frequent words (Fis- cher and Johanntokrax, 1995). In spite of their important quantitative role, discourse particles have so far been neglected in au- tomatic speech processing; if they are iden- tified at all, then only in order to eliminate them (O'Shaugnessy, 1993). Reasons may be firstly that it is not clear what they could contribute to the aims of automatic speech processing, and secondly that they may ful- fill so many different functions that it seems difficult to identify the information relevant to such aims. In this study, it will firstly be investigated what these discourse particles contribute to natural human-to-human conversation with the aim to determine which of their functions can be useful for automatic speech process- ing. In order to make use of the information they provide: however, they need to be dis- ambiguated. Two different strategies will be employed to disambiguate them automati- cally: On the one hand their position with respect to the turn and utterance in which they occur will be investigated in order to see how much it contributes to the interpre- tation of a discourse particle occurrence, on the other their role in the dialogue structure, especially regarding a dialogue model, will be analyzed. These two types of informa- tion, position and dialogue acts, are particu- larly easy to obtain during automatic speech processing. The aim of this investigation is thus to determine • what discourse particles contribute to hun~an-to-human dialogues; • what they may contribute to automatic speech processing; • in how far their surface properties, in particular their position regarding the 107 …

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