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Miller columns (also known as Cascading Lists) are a browsing/visualization technique that can be applied to tree structures. The columns allow multiple levels of the hierarchy to be open at once, and provide a visual representation of the current location. It is closely related to techniques used earlier in the Smalltalk browser, but was independently invented by Mark S. Miller in 1980 at Yale University. The technique was then used at Project Xanadu, Datapoint, and NeXT.
Contents
While at Datapoint, Miller generalized the technique to browse directed graphs with labeled nodes and directed graphs with labeled nodes and arcs. In all cases, the technique is appropriate only for structures with high degree (large fanout). For low-degree structures, outline editors or graph viewers are more effective.
History
Miller columns are most well known today as the “Columns view” mode of the Mac OS X Finder, as well as the "Browser" view in iTunes. The columns in Finder descend directly from the NeXTSTEP File Viewer's use of Miller columns going back to 1986. The GNUstep project continues to offer a Miller column browser that closely follows the NeXT approach, bringing the advantages of a Column browser to Linux, BSD, and other operating systems with large tree structures. The iPod's browsing of categories and audio file tag attributes is reminiscent of column browsing, but only one column is visible at a time.
Many software music players implement a "tag browsing" feature that utilizes Miller columns.
Issues
Miller columns have several issues from usability standpoint: