Pete Bell, from Endeca, makes an interesting observation about greying out non-relevant options when filtering with facets instead of hiding them. See his post “Search Facets: Bring Back the Dead Ends.” His example comes from the B&H Photo website, and it shows what Pete calls “grey ends” (as opposed to dead ends). He writes:
Gray ends are an exemplar of Edward Tufte’s advice to “always show comparisons adjacent in space rather than over time.” That is, if you want people to understand the difference between a “before” and “after” screen, when you redraw the screen, you’re asking them to rely on their memory to make the comparison. It’s always a risk to rely on memory, but it’s an even bigger risk here because we know people on the “before” screen were just focusing on the facet in which they made their explicit selection, rendering the others cognitively invisible. With gray ends, nothing has disappeared, so they get to compare the two states adjacent in space, no memory required. Tufte’s advice here is a classic for faceted UX work in general.
Grey ends make most sense with multi-select facets. The disadvantage is added complexity in the UI. Grey ends and multi-select facets aren’t appropriate for every situation, so I’d advise to use them with caution. Still, as Pete shows in his example, they can be a powerful addition to the faceted navigation experience.
I spotted grey ends a short while back on LinkedIn. This is also an example of multi-select facets, and it seems to work well. See the options in the Relationship facet on the left side of the image, below. After selecting a value from another facet, options in the Relationship facet turn grey.
Figure 1: Grey ends on LinkedIn (click to enlarge)
Finally, I also found Pete’s opening to his blog post interesting:
“There’s still so much room for innovation on faceted search user experiences.”
We’ve really just started to understand the intricacies of faceted navigation, I believe. Sure, Flamenco and other examples have made great strides. But there’s still lots more that can be done, particularly in real-world situations. Greg Nudelman’s example of Integrated Faceted Breadcrumbs I previously pointed to is just one example of the type incremental innovation that can take place in faceted navigation UIs.