Editor's note: This article was originally published in KM World, March 2009.
Stephanie is a Senior IA and Taxonomy Consultant with Earley & Associations.

Faceted search – keeping up with the Jones’

Faceted search, or guided navigation, has become the de facto standard for e-commerce and product-related websites, from big box stores to product review sites. But e-commerce sites aren’t the only ones joining the facets club. Other content-heavy sites such as media publishers (e.g. Financial Times: ft.com), libraries (e.g. NCSU Libraries: lib.ncsu.edu/), and even non-profits (e.g. Urban Land Institute: uli.org) are tapping into faceted search to make their often broad-range of content more findable. Essentially, faceted search has become so ubiquitous that users are not only getting used to it, they are coming to expect it.

Faceted search explained... briefly

Faceted search lets users refine or navigate a collection of information by using a number of discrete attributes – the so-called facets. A facet represents a specific perspective on content that is typically clearly bounded and mutually exclusive. The values within a facet can be a flat list that allows only one choice (e.g. a list of possible shoe sizes) or a hierarchical list that allow you to drill-down through multiple levels (e.g. product types, Computers > Laptops). The combination of all facets and values are often called a faceted taxonomy. These faceted values can be added directly to content as metadata or extracted automatically using text mining software.

The power of faceted search lies in the ability of users to create their own custom navigation by combining various perspectives rather than forcing them through a specific path. Think of a cookbook: authors have to organize the recipes in one way only – by course or by main ingredient – and users have to work with whatever choice of organizing principle that has been made, regardless of how that fits their particular style of searching. An online recipe site using faceted search can allow users to decide how they’d like to navigate to a specific recipe, offering multiple entry points and successive refinements. The diagram shows how facets can help pinpoint content very precisely through the combination of perspectives. Just 3 facets with 5 terms each can represent 243 possible combinations.

Combinatorial facets

Fig. 1: Combinatorial facets for a recipe site

As users combine facet values, the search engine is really launching a new search based on the selected values, which allows the users to see how many documents are left in the set corresponding to each remaining facet choice. So while users think they are navigating a site, they are really doing the dreaded advanced search – without the scary librarians-only interface.

Design dos & don’ts in faceted search

Now that faceted search interfaces are so prevalent, patterns are emerging that establish good design. If you are considering embarking on a faceted search implementation, here are 5 important points to consider:

Faceted search trends

As the trend towards increased social computing continues, Web 2.0 concepts are entering the realm of faceted search. We are starting to see social tags being used in faceted search and browse interfaces. Buzzillions.com, a product-review site, is using social tag-based facets in its navigation, allowing users to refine results based on tags grouped as “Pros” or “Cons”.

Combinatorial facets

Fig.3: Buzzillions.com faceted browse

This site uses a nice blend of free social tagging and control to ensure good user experience; when you type in a tag to add to a product review, type-ahead verifies existing tags and prompts you to select one from the existing list of matches to maximize consistency.

Doing it right

Ultimately, navigation and search is one of the main interactions users have with your site, so getting it right is not just a matter of good design, it impacts the bottom line. Faceted search is a very popular and powerful solution when done well; it allows users to deconstruct a large set of results into bite-size pieces and navigate based on what’s important to them. But faceted search by itself is not necessarily going to make your users lives easier. You need to understand your users’ mental models (how they seek information), test your assumptions about how they will interpret your terms and categories and spend time refining your approach.

Faceted search can just add more complexity and frustrate your users if not considered from the user perspective and carefully thought through with sound usability principles in mind. Faceted search is raising the bar in terms of findability and how well you execute will determine whether your site meets the new standard.

Want to Learn More on Organizing Your Site's Content?

Looking for ways to improve how your business is managing your critical information assets? UIE has asked Stephanie Lemieux and Seth Earley's to do our first UIE Virtual Seminar on this critical topic - New Ways to Think About Taxonomy: The Role of Taxonomies in Your Organization. Space is limited so be sure to sign up for the May 7 soon.

Share Your Thoughts with Us

Have you implemented faceted navigation in your web site? What challenges did you run into? Share your experiences at the UIE Brain Sparks blog at Brain Sparks Blog.

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