An LFG Grammar Checker for CALL

In this paper we present the possibilities of modifying an existing broad-coverage LFG for German in such a way that it can be used as a grammar checker in L2 learning that not only states whether or not the learner's input is grammatical, but also provides crucial information necessary for generating helpful feedback as to what has to be corrected. The necessary modifications, which consist basically in anticipating malrules, are exemplified with a number of notorious systematic errors L2 learners of German typically commit, such as the non-compliance of constraints on verb placement, the use of pragmatically inadequate constituent orders and agreement violations. At present, the modified grammar covers the most frequent error types of L2 learners. However, more corpus work is needed for extension and evaluation.