| The undo facility is an essential tool for graphical, direct-manipulation interfaces. Through the years, researchers have studied and proposed several types of recovery systems. However, due to several factors such as the complexity, cost, and usability of many of the novel approaches, the linear undo facility remains as the predominant recovery facility in today's interactive systems. This research studied, implemented, and evaluated an “object-based” recovery facility. In this system the undo/redo options or actions are associated and applied directly to the objects themselves. Furthermore, the undo options associated with each object are categorized according to the type of action. Results from a usability test showed that the tasks that required the undo or redo of previous or more distant actions were realized significantly faster with the “object-based” undo system. Regarding user satisfaction, the results reflected that 95% of the users preferred the “object-based” model over the linear model. |
