Haste-hierarchical abstractions in a system to teach electronics

One of the most promising, applications of computers in education is the use of simulations in training people to operate, understand or find faults in complex physical systems. There have been some attempts to base these simulations on qualitative models. However, such qualitative models at a single level of abstraction are inadequate for all but the simplest systems. What is required, for both graphical simulation and natural explanations, is the use of different sorts of abstraction. The most important sort of abstraction is structural abstraction, where modules, viewed as black boxes at one level, may be decomposed and explained at a more detailed level. The author describes the development of a system which allows people to explore a complex physical system on many levels. The most important feature of this system is the explanation facility which was developed following extensive analysis of human explanations and tutorial dialogues