The approaches to student modleing can be devided into three broad but distinct groups of thought:
Bug library technique Map the student's solution onto a predefined library of error types (Butron, Diagnosing bugs in a simple procedural skill)
Machine Learning approach Search the procedure space for a fitting model on-line. (Ohlsson, Langley, Psychological evaluation of path hypotheses in cognitive diagnosis)
Model Tracing technique follow the student step by step. (Anderson, Boyle, Corbett, Lewis, Cognitive modeling and intelligent tutoring)