Adaptive Interfaces in Mobile Environments 1 Running head: ADAPTIVE INTERFACES IN MOBILE ENVIRONMENTS Adaptive Interfaces in Mobile Environments - An Approach Based on Mobile Agents

ion of user interfaces adds flexibility when generating user interfaces. It provides a single and comprehensive description of the user interface. It is a rich layer of information that describes a user’s interaction with the computer. Such abstraction is formalized by using an abstract user interface definition language (Stottner, 2001) or task models (Limbourg & Vanderdonckt, 2003). This information can then be used to generate a user interface that meets a concrete platform’s limitations and requirements. Such an approach develops a single set of information to support all variants of the user interface that should be created for different devices. The user interface is typically abstracted through the use of design models (e.g., task models) or by using an XML-based abstract user definition language (Luyten & Coninx, 2001; Mitrovic & Mena, 2002; Molina, Belenguer & Pastor, 2003; Stottner, 2001). Task models (Limbourg & Vanderdonckt, 2003) provide information that is focused on tasks. Some of the task models can describe multi-modal tasks for different types of devices (Paterno & Santoro, 2002). However, task models do not necessarily specify the exact presentation of a user interface. On the other side, XML-based abstract user interface descriptions describe the user interface‘s presentation and constraints. Many different versions of such abstract user interface definition languages exist. Such approaches’ abstraction levels vary: some approaches include information specific to a device type (e.g., a mobile phone, or a specific mobile phone model), some are more generic and do not consider the specifics of any device type. In addition, user interface abstraction can differ conceptually—some models can define any kind of interaction (e.g., via voice or specialized interfaces), while some are more linked to specific concepts (e.g., window-based user interfaces). Examples of such abstraction languages include XUL, UIML, XIML and XForms (Stottner, 2001). The ability to effectively adapt such user interface definitions to a concrete platform is a key factor in achieving mobile and efficient user interfaces. The resulting, concrete user interface must meet the specification and be functional on the target device. This requires that device capabilities and limitations be successfully addressed. In addition, user preferences and context frequently impact this adaptation. abstract User interface adaptationUser interface adaptation User interface adaptation is a complex task, and includes not only adaptation to the specific device’s capabilities, but also to the user. Mobile devices have different capabilities such as screen size, keyboard and support for particular user interface widgets, hardware platform or operating system. Adaptation to a user includes adaptation to the user’s preferences and changing contexts, but sometimes includes factors such as previous knowledge or location. Platforms may have exceptionally different user interface capabilities and requirements (see Figure 1). In many cases adapting a user interface simply as a per user interface specification is not sufficient. For example, a combo-box widget as specified in the user interface description may be available on a particular platform, or not; there could be a similar widget or this widget should be transformed into a set of different widgets. To address this and to maintain the user interfaces’ plasticity (Thevenin & Coutaz, 1999) additional adaptation effort is required. User interface plasticity is a user interface’s capacity to preserve usability regardless of variations in the system hardware specification or operating environment. Adapting to users includes a wide range of considerations: users’ preferences, context, location, ambient environment, and so forth. This is a more complex transformation than adaptation