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Predictive Performance of Dialog Systems

This paper relates some of our experiments on the possibility of predictive performance measures of dialog systems. Experimenting dialog systems is often a very high cost procedure due to the necessity to carry out user trials. Obviously it is advantageous when evaluation can be carried out automatically. It would be helpfull if for each application we were able to measure the system performances by an objective cost function. This performance function can be used for making predictions about a future evolution of the systems without user interaction. Using the PARADISE paradigm, a performance function derived from the relative contribution of various factors is first obtained for one system developed at LIMSI: PARIS-SITI (kiosk for tourist information retrieval in Paris). A second experiment with PARIS-SITI with a new test population confirms that the most important predictors of user satisfaction are understanding accuracy, recognition accuracy and number of user repetitions. Futhermore, similar spoken dialog features appear as important features for the Arise system (train timetable telephone information system). We also explore different ways of measuring user satisfaction. We then discuss the introduction of subjective factors in the predictive coefficients.