Development and evaluation of the ATOS spontaneous speech conversational system

In this paper we report our development work in Spanish spontaneous speech conversational systems. We describe the automatic telephone operator service (ATOS) and present the improvements introduced into it to deal with spontaneous speech, which are: (a) a task independent dialogue manager, that can be adapted to a new semantic domain by changing a configuration file. It also generates a prediction about the user´s expected utterance to constrain the language model used by the speech recognizer; (b) a language modeling strategy, which allows to adapt the statistical language model to a new task with just few hundreds of sentences. This strategy reduces a 27% the word error rate. We also report the results, conclusions and the speech database collected in the evaluation of the ATOS system, which has been tested by 30 real users