A spoken dialogue system for German intercity train timetable inquiries

This paper focuses on the evaluation of the German Sundial Demonstrator maintaining interactive conversations via microphone and telephone with users. The word recognizer was implemented by the University of Erlangen and currently obtains on our test set a word accuracy of over 92% in a speaker{independent task with perplexity 111. We also participated in the design and implementation of the multilingual Dialogue Manager which is responsible for cooperative system behaviour. Over 100 prototype dialogues led to the current version which is continually being extended. The overall system performance is tested with semi{ naive users. Each subject faces four intercity train timetable scenarios, two of them are given, the others depend on the subjects' personal choice. Global system evaluation is done according to performance measures like contextual appropriateness, transaction success and dialogue completion rate.