Classification of user's knowledge into different levels ATTRIBUTES : STG (The degree of study time for goal object materials), (input value) SCG (The degree of repetition number of user for goal object materials) (input value) STR (The degree of study time of user for related objects with goal object) (input value) LPR (The exam performance of user for related objects with goal object) (input value) PEG (The exam performance of user for goal objects) (input value) UNS (The knowledge level of user) (target value)