A General Framework for Overlay Visualization

If visualization is more effective when accompanied by narration, why not superimpose visualization on narration? This might result in better transfer of learning. We will present a general framework for such superimposed visualization, called overlay visualization. The objectives for the design of our framework are 1) to separate the application from the visualization; and 2) to separate the specification from the rendering. We will describe a few applications of overlay visualization for programming and provide examples from our implementation of overlay visualization for software tutors called problets. The advantages of overlay visualization include: less cognitive load on the learner, and automatic support for both path and state visualization.