This is an update and extension to a previous post on showing more values in faceted navigation. First, I’d like to add one more approach to showing more values.
7. Overlay Dialog Window
Clicking a “more” link or “show all” link could open an overlay dialog window. This is similar to #4. Dynamic Menu mentioned in my previous post, but has an important difference. Namely, in this solution the items in the new dialog are not an extension of the default list of values. Instead, the list is presented again in its entirety. Subtle, yes–but it’s significant. For one, there is a greater transition to the new dialog window. This approach also allows for new order of values, if desired.
Presenting on overlay dialog window also differs from solution #3. New Page in my previous post. Instead of a page re-load, the new dialog is presented with the original page still in the background. So there is less transitional volatility from the original page and provides a better sense of staying close to the task as hand.
A key benefit of an overlay is increased real estate compared to dynamic menus and other solutions. It can essentially present the same amount of information as a new page. Ebay uses this solution for some of its facets, for instance for Brand shown in the figure below.
Figure 1: Example of an Overlay Dialog Window from Ebay.com
Second, inspired by Jason Hobbs’ talk at the IA Konferenz in Cologne, I did a literature search to find research on showing more values in faceted navigation. There is virtually no direct research on this topic. Indirectly, tests on Ebay have apparently shown that people are satisfied having a subset of all facet values presented by default with access to more . But how that access is provided doesn’t seem to have been studied.
One exception to this is the auto complete solution (#6 in my original post). Marti Hearst suggests that auto complete could aid in faceted navigation . She sites general studies of auto complete to begin [3, 4] and assumes these are effective approaches: “This is a rare case in which there have been few if any usability studies … but by observation and anecdote, I am willing to claim that the usability appears to be very high.” Bast and Weber  carried out a specific investigation into auto complete with facets. Their findings suggest that there is improved search times when using auto complete, but they did not investigate the interface solution presented in my example using LinkedIn, nor as found in Semedico (see my original posting).
If you are aware of any research on how to best show more values in faceted navigation, please let me know. Until, designers will have to rely on their design reasoning to arrive at usable and innovative solutions.
 “Faceted Metadata for Information Architecture and Search,” CHI Course for CHI 2006, by Marti Hearst and Preston Smalley, and Corey Chandler of eBay.
 “UIs for Faceted Navigation: Recent Advances and Remaining Open Problems,” in the Workshop on Computer Interaction and Information Retrieval, HCIR 2008, October 2008, Redmond, WA, by Marti Hearst.
 H. Bast and I. Weber. “Type less, find more: fast autocompletion search with a succinct index.” In Proceedings of the 29th annual international ACM SIGIR conference on Research and development in information retrieval, pages 364–371. ACM New York, NY, USA, 2006.