CONVERSATION AND DISCOURSE
Though natural-language processing encompasses a broad range of linguistic phenomena, a central goal that is often cited in both the technical and the popular literature is the production of a human-like dialogue interface. In some ways, the notion of a computer with which one could carry on an ordinary conversation represents the ultimate aim of all research in natural-language processing.
Many existing computer systems use some form of natural language to communicate with users and are therefore referred to as "dialogue systems." This might lead one to believe that with suitable enhancements, such as an increase in vocabulary, syntax rules, or semantic memory, these systems could be upgraded to the level of human performance. Unfortunately, this is not so. Unlike current machine-dialogue interfaces, natural human conversation is part of an intricate web of cognitions and intentions that constitute the foundation for all symbolic communication. Utterances themselves are merely the surface manifestations of nonlinguistic phenomena such as plans, beliefs, goals, and so forth. Systems that process only the surface linguistic features of a dialogue will never be able to achieve even a rudimentary approximation of genuine dialogue behavior.
This fact has prompted conversation and discourse research to move far away from traditional issues in naturallanguage processing and to adopt a perspective that differs