Defining the Mobile Style

The user interface of a mobile phone extends beyond hardware and software-to the sales package, documentation, customer help lines, and even repair centers. Here we will focus on hardware and software and their interaction. The hardware UI is created by industrial and mechanical designers who lay out keypads, control devices and display modules, design the snap-on cover mechanisms and accessory connectors, and wrap this all into an appealing package with the right shapes, materials, and colors. The software UI is created by interaction designers, graphic designers, and software engineers who define the interaction logic and control key combinations, lay out menu structures, design the graphics and sounds, localize the display texts, and implement it all in embedded or downloadable software. This little-understood enterprise can be divided into user interface style and user interface features.

The UI attributes presented in Table 1.1 are the guiding factors in any UI design process for mobiles, whether the designer is working on a new style or on a new feature. An expression style mobile like the Nokia 3330 demands a user interface different from that of a classic style phone such as the Nokia 6610, because the customers and product drivers are different. Therefore UI style becomes the backbone of a phone's user interface. It is

the basic framework for how the user operates the phone, how the menu structure is navigated, and how information is displayed. UI features for the phone-applications such as phonebook, text messaging, or FM radio-come second and are designed to comply with this framework.

This definition of UI style is peculiar to the domain of cellular mobile phones. Donald Norman,^[1] the perennial analyst of how things work, discusses a slightly broader domain of interactive and intelligent devices and talks about smart products and information appliances, respectively. Deborah Hix and H. Rex Hartson^[2] approach the concept of user interface style from a broader human-computer interaction perspective and define UI style as follows: 'A user interface style is a design framework describing interaction style and objects, including appearance (look) and behavior (feel).'

Nokia's internal definition follows:

The user interface style is a combination of the user interaction conventions, audiovisual-tactile appearance, and user interface hardware.

Let's break that down to its components. User interaction conventions describe how input functions are mapped to output functions. Audiovisual-tactile appearances define sensory elements of the user's experience, and how those elements are used in accordance with user interaction conventions. UI hardware includes display modules, keys and keypads, vibration motors, speakers, sensors, and anything else that makes UI conventions functional and appearances physical. Traditionally, UI conventions are dictated primarily by the hardware control keys and appearance is dictated largely by visual attributes such as graphical layouts. We are now in the process of gradually moving toward a richer user experience with elements such as vibration feedback and polyphonic audio.

We cannot sell UI styles, however, no matter how well informed they may be. The customers are paying for certain features and functionality, and the role of the UI style is to facilitate the creation and integration of a consistent and usable set of these features and functions. New UI styles are legitimately created only in response to some specific customer needs, or to solve real or anticipated problems in an existing UI style. Even then, new styles are not created lightly. An example of compelling customer needs could be a newly identified consumer category or discovery of a specific market with unfamiliar requirements-perhaps the requirement to support a new writing system. An example of anticipated problems could be the incorporation of a new UI technology-say, digital imaging-that has an unintended impact on the original UI.

Clearly defined and documented UI styles are all the more important to a global, multisite R&D community such as Nokia. It's commonplace for a large team of UI designers to be working on a single product and its applications from several continents. These people come from different cultural backgrounds and have different levels of UI design experience. The UI style is the framework for the product's UI that will keep the overall user experience consistent and appealing despite that diversity. Styles are constructed from a specific set of fundamental UI components, and all applications are designed and assembled using these components so that functionally-or structurally-similar kinds of applications look and feel the same.

^[1]The 3110 product announcement from Nokia (available at http://www.nokia.com/news/news_htmls/nmp_970312b.html ) presented the user interface as the most distinctive feature of the new product: 'The most distinctive feature of the new Nokia 3110 is its smart menu system. The smart Navi-Key allows fast, one-button access to the functions of the phone, another industry-first innovation from Nokia. Upon pressing the Navi-Key, the phone guides the user through the features, providing fast and easy operation.'

^[2]2G GSM high-speed circuit-switched data (HSCSD)-up to 57.6 Kbps; 2.5G GPRS-up to 171.2 Kbps; 3G WCDMA-up to 2 Mbps. For further explanation of this technojargon, please see Glossary.