Schema method: a framework for correcting grammatically ill-formed input

The schema method is a framework for correcting grammatically ill-formed input. In a natural language processing system ill-formed input cannot be overlooked. A computer assisted instruction (CAI) system, in particular, needs to show the user's errors. This framework diagnoses ill-formed input, corrects it and explains the error, if an input is ill-formed. The framework recognizes a sentence at two steps: first parses weak grammar, and then strongly filters the parsed sentence. When it is known what sentences are passed by the filter, it can be used even if it is imperfect. As the strong filter, a new method is used: an interpretation schema and an interpretation rule. An interpretation schema collects input information schemata and then an interpretation rule judges whether the collected schemata are correct or incorrect. This approach overcomes the problem of relaxation control, the major drawback of the previous syntactically-oriented methods, and is also more efficient.