Spoken Language Dialogue Systems

Abstract

The dream of having computers able to sustain free conversations with humans has begun to become a reality in the last few years, when, thanks to significant advances in the fields of speech and language processing and to the advent of fast processing machinery, the first working prototypes of spoken dialogue systems have been built. More recently, we are now seeing these systems being further developed into real applications. The system we are referring to in this chapter have a number of common features:

• 1. They work within a limited semantic domain (e.g. database inquiry about a specific subject);

• 2. They have a limited vocabulary (of the order of 1000 words), which is sufficient to support essential dialogues in these domains;

• 3. They are designed to work for the general public rather than for trained users. In particular, we refer to systems developed for use on the public service telephone network (PSTN) by casual, ‘naive’ users (as opposed to regular, ‘experienced’ users). Consequently they have to deal with so called ‘spontaneous speech’ (continuous speech, irregular sentences, ungrammaticalities, extralinguistic phenomena, etc.);

• 4. Freedom of dialogue is limited and the control is taken by the machine whenever problems of understanding occur.