Int J Speech Technol (2008) 11: 209–221 DOI 10.1007/s10772-009-9052-6 Modelling dialogue as inter-action Gemma Bel-Enguix · M. Dolores Jiménez-López Received: 14 July 2009 / Accepted: 26 October 2009 / Published online: 12 November 2009 © Springer Science+Business Media, LLC 2009 Abstract In this paper we introduce a formal model of di- alogue based on grammar systems theory: Conversational Grammar Systems (CGS). The model takes into account ideas from the study of human-human dialogue in order to define a flexible mechanism for coherent dialogues that may help in the design of effective and user-friendly com- puter dialogue systems. The main feature of the model is to present an action view of dialogue. CGS model dialogue as an inter-action, this is a sequence of acts performed by two or more agents in a common environment. We claim that CGS are able to model dialogue with a high degree of flexi- bility, which means that they are able to accept new concepts and modify rules, protocols and settings during the compu- tation. Keywords Dialogue modeling · Formal language theory · Dialogue management · Conversational grammar systems 1 Introduction Human-computer interaction (HCI) did not exist as a field of scientific inquiry in the earliest days of computers because very few people interacted with computers, and those who did generally were technical specialists. Papers on the topic began to appear only in the 1960s. As more and more people G. Bel-Enguix ( ) · M.D. Jiménez-López GRLMC-Research Group on Mathematical Linguistics, Rovira i Virgili University, Av. Catalunya, 35, 43002 Tarragona, Spain e-mail: gemma.bel@urv.cat M.D. Jiménez-López e-mail: mariadolores.jimenez@urv.cat found themselves using computers for a broadening variety of tasks, the topic became an important focus of research. HCI has now become a major area of research in computer science, human factors, engineering psychology and closely related disciplines. According to Ogden and Bernick (1997), a goal of hu- man factors research with computer systems is to develop human-computer communication modes that are both error tolerant and easily learned. Since people already have exten- sive communication skills through their own native or nat- ural language, many believe that natural language interfaces can provide the most useful and efficient way for people to interact with computers. Taking into account this idea, what we propose in this paper is to start by the study and analysis of spoken human-human dialogues in order to abstract their main principles and mechanisms and to apply them to the definition of a formal model of dialogue that may be used for designing effective, efficient and user-friendly computer dialogue systems. Research on dialogue has been largely absent from aca- demic disciplines till the second half of the 20th century. The importance of dialogue was discovered by an empirical discipline, known as Conversation Analysis, that emerged in the early 1960s within the field of ethnomethodology. The main purpose of that research stream—always related to the names of Sacks, Schegloff and Jefferson—can be stated quite simply: to describe the ‘technology of dialogue.’ The most important objective of conversation analysis is to ex- plain procedures used by participants in a dialogue to pro- duce utterances and to make sense of other people’s talk. Be- ing concerned with talk as a collaborative matter and with how parties can jointly produce an organized sequence of talk, conversation analysis tries to specify how the consec- utive actions that dialogue consists of are related one to another and how they build up a conversational sequence.