Design Patterns for Mobile Faceted Search: Part I

Four Corners and Modal Overlay Patterns

As I described in my column “Search Results Satori: Balancing Pogosticking and Page Relevance,” maximizing the number of results on a search results screen is key to improving information scent and overall finding efficiency. One of the most successful design patterns for maximizing the use of screen real estate is the Four Corners pattern, shown in Figure 4.

The Four Corners pattern devotes almost the entire mobile screen to search results. Users can display particular functions by tapping the semitransparent corners, which provide access to filters, the home page, and two additional menus. This pattern includes a thin, persistent status bar across the top of the screen, which displays an entire search query, plus any applied filters, rather than just the few characters Amazon Mobile displays in a large font. Displaying an entire query is highly beneficial, given users’ mobile context of use and the frequent interruptions inherent in the mobile finding experience.

Although the design pattern is called Four Corners and triangles are the most effective shape for the corners, they don’t necessarily have to be triangles. Other alternatives include semitransparent buttons or floating icons. However, for transparent buttons, it’s best to keep icons simple and avoid text labels.

Another pattern that works really well with Four Corners is the Modal Overlay pattern, shown on the right in Figure 4. A modal overlay can display various search-refinement options such as filtering and sorting. As I wrote in “The Mystery of Filtering by Sorting,” it is not necessary to place filtering and sorting in two different areas of a screen. Most people have, at best, just a vague idea of the differences between the two features. This is particularly true for the mobile experience, where screen real estate is at a premium and minimizing the number of taps necessary to achieving a goal is key.

The Four Corners and Modal Overlay patterns work particularly well in combination. In Figure 4, each user interaction on the modal overlay refines the search results interactively. This dynamic interaction model works great, because users can always see where they are and what filters they have applied, and they have easy access to further refinement options, all without ever leaving the context of the search results screen.

Some touch phones—like the iPhone—do not provide an API (Application Programming Interface) for modal overlays, but instead deliver content one screen at a time, with transitions between screens. On such devices, you’ll need to fake modal overlays. You can achieve this effect by rendering the same search results on a new screen—this time with a slightly darkened background—with a modal overlay over the results. When displaying this new screen, an application should minimize any transition to help to preserve the illusion of maintaining the search results context.

Watermark Pattern with the Full-Page Refinement Options Pattern

The latest generation of smartphones—including the Apple iPhone, Palm Pre, and Google Android—provides designers with a whole bevy of novel interaction models. Some of the ways in which people must interact with new smartphones may not be obvious to them, because they may not match their existing mental models or the affordances of devices with which they’re familiar. Nevertheless, once people discover these interactions, they seem surprisingly intuitive and fun, and people do not easily forget them.

In mobile computer games, it is common practice to teach players by allowing them to manipulate their mobile devices through various gestures, including tilting, turning, and shaking them—or even using a device’s accelerometer to mimic the way one would use a magic wand: “Incendio!”

In ecommerce applications, customers’ object in interacting with a mobile device is not typically entertainment, but the efficient acquisition of goods, services, or information—so necessity typically shortens their learning curve. If we want people to be able to perform a nonstandard interaction to use a device’s essential features, the interaction must be fairly obvious—and it must not require them to read instructions they would perceive as obnoxious or distracting. This is where careful use of the Watermark design pattern can be especially powerful.

A watermark is a transparent outline that appears either over or behind the primary content on a screen. In some ways, a watermark is similar to a splash screen, but it is considerably less distracting because watermarks let users see the content on the screen at the same time. Figure 6 shows two variations of the Watermark pattern, plus a full-screen example of a Refinement Options pattern.

The two examples of the Watermark pattern, shown in Figure 6, demonstrate a circular swiping gesture and a shaking gesture on a multitouch device. In both cases, once a user launches an application, each watermark appears just once or twice, gently dissolving to let the user view the screen’s main content. Watermarks can also use animation—for example, to demonstrate the motion of the circular swipe by displaying one arrow at a time on the screen. However, animation greatly increases a watermark’s visibility, so you should use it with care. Circular swiping emulates the motion of digging into a pile of puzzle pieces to find the right one, while shaking recalls the action of shaking up small, loose objects in a bag or a box.

In each case, the idea behind the watermark is to educate or remind people about the gesture or interaction that is necessary to view a screen containing additional search-refinement features. Once people decide to dig in further or shake up their search results, the application displays a full screen of refinement options, as shown at the bottom of Figure 6. This screen provides an example of the Refinement Options pattern. Again, the thin, persistent status bar across the top of the screen shows the query. Together with the watermark, this helps maximize the real estate the screen can devote to search results, while making exploration intuitive.

With a full screen of refinement options, a user can view four or five of the most popular values for each of the facets and select a facet value with a single tap. This is almost like having the entire array of refinement options on a typical faceted search results Web page. Having the search box integrated into the refinement options page also re-enforces the idea of applying search query terms and facets together as a set, just as they are on a Web page. Together, these patterns let us duplicate the intuitive and efficient step-wise refinement and expansion flow our customers expect from a faceted search results page on an ecommerce site. Using a scrollable screen of facets rather than a modal overlay like that shown in Figure 4 allows us to devote the full screen width to the search results, sprucing them up with icons for popular refinement options and letting customers refine the results with fewer taps.

Does this mean presenting a full page of refinement options is better than a modal overlay? Not at all. A modal overlay displays its refinement options within the context of the search results, while displaying a separate results-refinement screen, along with its associated transition, yanks customers out of the search-results context and presents what some people might think is an overwhelming variety of refinement options.

When discussing design patterns, avoid getting caught up in judging one pattern to be better than another. Each pattern is useful in specific contexts and applications and for particular purposes and types of customers. Design patterns are like a language we can use to communicate with our customers. It helps to have a vocabulary of patterns that is as complete and varied as possible, as well as to use each pattern appropriately to communicate your design message with clarity and precision. 

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Design Patterns for Mobile Faceted Search: Part II