Incorporating confidence measures in the Dutch train timetable information system developed in the ARISE project

The use of confidence measures (CMs) in spoken dialog system (SDS) applications to suppress the number of verification turns for 'reliably correctly recognised utterances' can greatly reduce average dialog length which enhances usability and increases user satisfaction. This paper gives a clear review of the method of CM assessment, which was presented by Boves, Herberts and Russel (see Proceedings of the IEEE Third Workshop Interactive Voice Technology for Telecommunications Applications, Granada, Spain, p.89-92, 1996). It proceeds by demonstrating how the Dutch ARISE (Automatic Railways Information Systems in Europe) SDS was equipped with this technology and shows in deep detail how the parameters involved are to be optimised. The evaluation reveals and explains a typical behaviour of this method with train timetable information-alike systems. This results in a set of conclusions that were not foreseen when the method was first developed for a directory information system. The paper ends with an outlook for solutions in new research directions.