An Educational System that Explains the Domain-oriented-explanation of Program's Behaviors

We have developed an educational system that helps novice programming language learners. Our system can output the verbal and visual explanation that explains the behavior of a program on the domain world. When learners input their own program that has a few bugs, they can spontaneously notice that there are a few bugs in their program by referring the explanation contradictory to their expectations, and try to fix them.