In this paper, experimental results of evaluating dialogue strategies of confirmation with a noisy channel are presented. First, the types of errors in task-oriented dialogues are investigated and classified as communication, dialogue, knowledge, problem solving, or objective errors. Since the errors are of different levels, the methods for recovering from errors must be examined separately. We have investigated that the dialogue and knowledge errors generated by communication errors can be recovered through system confirmation with the user. In addition, we examined that the manner in which a system initiates dialogue, namely, dialogue strategies, might influence the cooperativity of their interactions depending on the frequency of confirmations and the amount of information conveyed. Furthermore, the choice of dialogue strategies will be influenced by the rate of occurrence of communication errors in a communication channel and related to the properties of the task, for example, the difficulty in achieving a goal or the frequency of the movement of initiatives. To verify these hypotheses, we prepared a testbed task, the Group Scheduling Task, and examined it through a computer-to-computer dialogue simulation in which one system took the part of a scheduling system and the other system acted as a user. In this simulation, erroneous input for the scheduling system was also developed. The user system was designed to act randomly so that it could simulate a real human user, while the scheduling system was devised to strictly follow a particular dialogue strategy of confirmation. The experimental results showed that a certain amount of confirmation was required to overcome errors when the rate of occurrence of communication errors was high, but that excessive confirmation did not serve to resolve errors, depending on the task involved.

This paper describes the development of an environmental ICAI system for English conversation learning, which is equipped with a simulation-based learning environment and an advisor function. Recently there have been various educational applications or tools for adult second language education, where the learning target is the acquisition of formal knowledge of a language. When considering the implementation of a practical CAI system, methods for developing communicative competence in learners are required. Although there are a number of ICAI systems for conversation learning, often the methodologies which they apply are not completely suitable for the acquisition of the required fundamental knowledge. Our system, based on the architecture of environmental CAI, enhances communication skill acquisition. The system has a learning environment with the following features: (1) A simulation of language activities, implemented in the role-playing game style, which helps to promote a learner's motivation. (2) Educational behavior of the system is varied through the modification of the learning environment and changes in the simulation progress and control commands. (3) An induction strategy, which can cause learners to fail to achieve a learning target, is executed by an advisor mechanism. The system is a prototype architecture for application in environmental ICAI systems for simulation based learning. We believe that the architecture of this system is an efficient framework for linguistic education.