Benjamin Bederson, Aaron Clamage, Mary Czerwinski, George Robertson
Calendar applications for small handheld devices are growing in popularity. This led us to develop DateLens, a novel calendar interface for PDAs designed to support complex tasks. It uses a fisheye representation coupled with compact overviews and animated transitions to give a big picture in a small space. The interface also gives users control over the visible time period, as well as supporting integrated search to discover patterns and outliers. Designed with device scalability in mind, DateLens runs on desktop computers as well as PDAs.
Two user studies were conducted to examine the viability of DateLens as a replacement for traditional calendar visualizations. In the first study, non-PDA users performed complex tasks significantly faster (12 percent) with DateLens than with the Microsoft Pocket PC 2002 calendar (using a PDA emulator). In addition, they rated DateLens as being easier to use than the default calendar application for a majority of the tasks. In the second study, the participants were expert Pocket PC users and the software was run on their own devices. Again, DateLens performed significantly faster (17 percent) for the complex tasks, and there were satisfaction differences favoring each calendar for different kinds of tasks.
From these studies, DateLens appears to be superior for more complex tasks, such as those associated with longer time periods. But for daily event tracking, users familiar with the default Pocket PC calendar strongly preferred its daily view and behaviors. Based on some DateLens usability problems that were observed, we are confident that DateLens could perform better than it did in the studies for simple tasks. There doesn't appear to be any conceptual reasons that DateLens could not support the "simple" tasks as well as the Microsoft calendar, yielding a solution that is better in all cases.
Our understanding of the reason for the difficulty of the complex tasks is that those tasks require comparison between multiple dates, and an understanding of a large expanse of time. In order to do these things, traditional calendar designs require users to switch between the different views (day, week, month, and year)keeping the relationship between dates in their heads. That is, we believe that traditional calendar designs require greater use of short term memory to solve more complex tasks. By showing a visual representation of dates in context with animated transitions, users appear to be able to compare multiple dates across larger expanses of time with reduced memory load.
A remaining important question is that we don't know where fisheye distortion displays are likely to be useful outside of the domain of calendars. We can answer this only with our intuition; we found that the key characteristics of our solution that made DateLens work were:
- A simple navigation mechanism: All nodes are visible and a tap always expands a node.
- A simple representational structure: The familiar tabular representation of calendars made a grid a natural representation for us to follow.
- Clear small representations of data: It is crucial that all data has some meaningful representation that can fit in a tiny space.
DateLens is available at www.cs.umd.edu/hcil/datelens
Human-Computer Interaction Laboratory Computer Science Department, University of Maryland, College Park
Benjamin B. Bederson
Mary P. Czerwinski
George G. Robertson
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