  This paper presents Dialogos, a real-time system for human-machine spoken
dialogue on the telephone in task-oriented domains. The system has been tested
in a large trial with inexperienced users and it has proved robust enough to
allow spontaneous interactions both to users which get good recognition
performance and to the ones which get lower scores. The robust behavior of the
system has been achieved by combining the use of specific language models
during the recognition phase of analysis, the tolerance toward spontaneous
speech phenomena, the activity of a robust parser, and the use of
pragmatic-based dialogue knowledge. This integration of the different modules
allows to deal with partial or total breakdowns of the different levels of
analysis. We report the field trial data of the system and the evaluation
results of the overall system and of the submodules.
