A system for man-machine communication using speech

Abstract

KEAL is a continuous speech recognition system developed at the CNET laboratory in Lannion (France). Part of the laboratory's current work aims at extending it in the direction of a speech-understanding and man-machine dialog system. A question-answer-type dialog is set in motion in order to provide the user with information (the current application consists in simulating a directory inquiries service). This paper describes how syntactic, semantic and pragmatic knowledge is used for implementing such a dialog, and the main advantages and drawbacks of the methods chosen are discussed. Sentence recognition is performed by a left-to-right bottom-up parser by means of a semantic context-free grammar. Using a method analogous to that of semantic attributes, the parse-tree is then interpreted in order to obtain a semantic structure which represents the information relevant to the subsequent dialog. The dialog manager uses the semantic structure for instantiating a model graph, which represents the state of the dialog at any instant; it indicates the next message to be sent to the user, and how to analyse his answer.An example derived from the directory inquiries service is described.