Interpretation of ungrammatical sentences in a language education system for nonnative speakers

In learning foreign languages, especially when the learners want to polish their conversation skills, they need to put themselves in a variety of situations where they perform various tasks in their target languages. Conventional language education systems offer exercises for fixed phrases or conversation practice using predetermined dialog patterns. Ideally, the learners should participate in a dialog that dynamically changes in accordance with the utterances of the participants, and they should decide what to say by themselves according to the changing environment. Such a learning environment needs a teacher to participate in the dialog and help the learners continue the conversation even if their utterances are ungrammatical. This research aims to construct a system that plays a teacher role of this kind. This paper is concerned with how to develop a system that accepts and interprets both grammatical and ungrammatical inputs.