October 21, 2010
Displaying multiple levels of data visually has been proposed to address the challenge of limited screen space. We review 22 existing multi-level interface studies and cast findings into a four-point decision tree: (1) When are multi-level displays useful? (2) What should the higher visual levels display? (3) Should the visual levels be displayed simultaneously? (4) Should the visual levels be embedded, or separated? Our analysis resulted in three design guidelines: (1) display and data levels should match; (2) high visual levels should only display task-relevant information; (3) simultaneous display, rather than temporal switching, is suitable for tasks with multi-level answers.