Dialogue Processing in a CALL-System

In a CALL-environment (Computerassisted language learning) programs should ideally allow the learner to train his/her communicative competence, which is one of the main goals of foreign language teaching nowadays. This can be reached by allowing learners to use and train their knowledge of a foreign language in realistic dialogue-style exercises. All levels of linguistic and communicational analysis have to be considered to realize such a system. In this paper I will concentrate on the dialogue component of the concept, which relies on two main knowledge sources. The discourse grammar structures the dialogue elements (or dialogue acts) as possible parts of a dialogue and the dialogue knowledge base provides the possible contents of dialogues. Additionally, a framing discourse structure has to be built to provide the specific dialogue-exercise. A FSA (finite state automaton) based on the discourse grammar determines the possible moves which the dialogue might take. On the one hand this concept is restricted enough to allow for (relatively) easy maintenance as well as expansion and on the other hand it is advanced enough to allow for simulated complex dialogues. 1 I n t r o d u c t i o n Today the main goal in foreign language teaching is acquiring the so-called communicative competence instead of only memorizing the structure of the language. This can be achieved by making active language production one of the main parts of the curriculum. Being an efficient part of the media to enhance the learning process, computers should present tasks that support the acquisition of communicative competence. In the present concept, a presentation of situations is suggested, in which the learner has to produce language, i.e. produce complete sentences in a simulated dialogue. Various program modules analyse the input linguistically, give feedback in case of errors and present appropriate reactions to continue the dialogue. This gives language learners a chance to use their knowledge of the second language in a meaningful situation apart from the class room setting. Three goals are of relevance: 1) the language learner should be encouraged to enter free-formed input instead of thinking about the 'expectation' of the program; 2) the program should offer reliable feedback to the learner about his/her performance and 3) the program should be (easily) expandable. When one uses the program, a situation is presented to the learner in which s/he is required to act in order to solve the particular problem at hand. For example, the learner is asked to buy tickets for a movie and has to engage in a written dialogue with the computer as the seller of the tickets. The motivation for the development of the system arises from the above mentioned pedagogical considerations and the insight that traditional language learning programs do offer only few or none of the features to reach the above mentioned goals. The main part of this paper, however, deals only with the computational aspects of the problem: a possible way to implement such a dialogue component. In the next section I will focus on the dialogue component, which on the one hand allows the learner to communicate with the computer in various dialogue situations, and on the other hand is restricted enough to be easily expandable and maintainable and gives the possibility for advanced feedback. Finally I will give a