Faceted search results differ from traditional searches by way of the facet categories which are displayed on the search results. These facets are sometimes called search options or content categories — depending on who you ask — and reflect the similarities shared between the search results. This allows you to not only search for glasses, but view all of the results that are new, or inexpensive, or blue.
Google has recently added a number of facets to their search results. You can view these by clicking Options on the search results page (directly below the Google search bar). These options (aka Facets) allow you to view the Video results of your search, or to view the results in a time line or a wonder wheel that is really fun to play with — if you’re into the whole data visualizing thing:
My favorite faceted searches stack the facets directly above the results. So to begin with, the user sees their search term and the number of results that it has produced. When they click on a facet to view all the new things, that facet appears above the search results, directly below the search term. To remove a particular facet from the top of the page, users simply need to click an X at the end of each line:
As for the facet controls themselves, remember to think outside of the standard form. You could use a map widget instead of an address form to locate an area on a map. For short numerical ranges, a slider can feel more natural when it comes to increasing or decreasing values. If you’re feeling particularly adventuresome, charts and graphs can also be used to illustrate certain facets of the results.
One final point I feel compelled to make is the fallacy of the three point click in relation to faceted searches. Facets enable users to explore the data instead of desperately searching for that one result which contains all of their answers. Just imagine a Wiki adventure where one answer brings up new questions and allows you to explore the alternatives.
For more information about faceted searches, I recommend UIE’s virtual seminar on Faceted Search: Designing Your Content, Navigation, and User Interface. They also include some handy information on design patterns that I am sure to be sharing before long! For those of you without a few hours to spare on the seminar, you can download a PDF handout of their presentation.