A learning system uses the concept of template automaton. "Various expected examples of learners" consisting of "correct" answers and "incorrect" answers are collected and a representative NLP technique such as HCS (heaviest common character string) or LCS (longest common character string) algorithm is used as an effective error diagnosis engine in the language learning system. These examples embedded in the template are used for diagnostic analysis of the answers of the learners. This diagnosis is performed by selecting a path of the highest similarity with the input sentence of the learner among a plenty of candidate paths. Thus, it is possible to automatize and simplify the time-requiring authoring task used in the language-oriented intelligent learning system.