An empirical evaluation of undo mechanisms

While various models of undo have been proposed over the years, no empirical study has yet been done to discover which model of undo most closely aligns with what users expect an undo command should do. In this paper, we discuss the results of such a study that compares the ubiquitous linear undo model with two variations of selective undo: script selective and cascading selective. Unlike the script model, cascading selective undo takes into account dependencies between user actions. Our study shows that, for the application studied, when a user is asked to perform undo in the absence of any guidance, the user will tend to gravitate toward an undo mechanism that uses existing dependencies between user actions. Specifically, we show that subjects prefer the dependency-aware aspects of cascading undo over either linear or script selective undo.