Grammars as user models

This paper describes how grammars of native languages can be used is tutoring systems to facilitate instruction in a second language. The grammar functions as a user model, which enables the system to customise its responses by addressing problems that may be due to interference from the native language. Its correction strategy is based upoa comparison of the native language model with a model of the target language. The problems and solutions presented in this paper are related to the more general question of how modelling previous knowledge facilitates instruction in a new skill.