It is a vital and challenging issue in AI community to get the "Right Information" to the "Right People" in the "Right Language" in the "Right Timeframe"in the "Right Level of Granularity". More and more researchers recognized that a well-designed instructional plan in intelligent tutoring systems will open up new possibilities of genuinely intelligent knowledge delivery for future education society. This paper proposes a novel three-layer student-state model and discusses the core elements in the architecture of a practical ITS model based on the theory of instructional automata. The main advantages of instruction automata theory lie in that it can not only generate, regulate, update and implement instructional plans for individualized learner in the efficient and effective way, but also provide a uniform and extensible domain-independent environment for ITS designers and engineers.