Treemaps Bloom

Computerworld - A second spring is blooming for a uniquely visual interface that lets users view thousands of files at once as proportionately sized rectangles, grouped to represent folders.
These "treemaps" will see increasing use in applications that can give users a fast yet comprehensive understanding of complex structures, developers say.
Treemap developers from across the U.S. and Europe met at the University of Maryland, College Park, in June to share research results.
New algorithms offer improvements. They maintain ordering, such as by size, alphabet or date created; reduce surprising movements of file images as sizes change; and prevent having a screen with hundreds of razor-thin slices and a handful of squares.
New "squarification" algorithms ensure that all files will be represented as squares. One application adds color and 3-D shading techniques.
An open-source Java treemap library, a work in progress, is downloadable for free.
"We were thrilled to see how people have started with our basic idea and taken it past where we dreamed it might go," says Ben Shneiderman, a University of Maryland professor who 11 years ago built the first treemap (www.cs.umd.edu/hcil/treemaps/treemap2001).
The first treemaps used a simple slice-and-dice algorithm that sometimes produced arbitrary and extreme shapes. The newer squarification algorithms assign space based on the weight of the attribute selected - such as size or most recent date of alteration - and arrange the resulting file images to give a more square look to each group.
Hip to Be Squarified
New York-based SmartMoney.com has incorporated a squarified treemap view in its MapStation application at www.smartmoney.com/ mapstation. Stocks are represented by colored rectangles, and traders can make size and color represent any of several dozen financial indicators. For example, size can represent a stock's price at the moment, while color can indicate whether a stock's performance that day is hot.
In ordered treemap applications like SmartMoney's, users can select a "pivot point" based on a file attribute such as median size. All file images will be sized in relation to the pivot file's designated size. Views that use this kind of pivot point tend to offer smoother update views, an important consideration when the treemap must present the results of dynamic queries, such as in a photo-browsing application.
In developing his PhotoMesa photo browser, Ben Bederson, director of the Human Computer Interaction Laboratory at the University of Maryland, faced a visualization problem new to treemaps. A photo file size may vary, depending on resolution, but all photos must be represented at equal size, although their orientation may be landscape or