Chapter 6: User Interfaces for Mobile Media 249 with the current view, or with the application – and how to design the interaction is affected by the available input devices. Also, the current context affects the presentation and interaction: if the user is walking, they cannot manipulate a long list easily, while using a speaker and text synthesis would not be socially acceptable in a theatre. How to provide and access functionality? In addition to implying what are the available actions or content object(s) relevant to the task, the question relates to aiding navigation between the objects and controls. How to perform an action or operation depends on many factors. If the action is performed frequently or the designer wants to highlight some core functionality, a hardware key can be assigned instead of using a menu. In essence, the different levels of functionality are: • What operations are available for the highlighted object in the view? • How the objects in the view can be organized (for example, ordered, fi ltered, or highlighted)? Can the type of the view be changed (from list to grid)? • What application level operations are available? For instance, search, settings, shortcut to another application (go from camera to image gallery). • Current state of the system (change WLAN access point). How to navigate between the UI parts? Considering navigation in a single view or even in one application is not suffi cient, since the user may need to perform multiple tasks at the same time and thus switch between the active applications. The defi ned unique operations are required for designing the dia- logue and the structure of the application. The aim of the structure specifi cation is to place operations into states and depict the relations, or required navigation steps, between them. It is essential to provide fast and easy access to primary tasks(s) and related operations and thus, the main operations should be performed in the primary (main) state. Secondary operations, which support performing the main task(s) or are performed less frequently, are divided into secondary states. The structure of the user interface can be visualized with a dialogue diagram that presents the states and related operations and transitions (relations) between the states. In order to illustrate the design process, we now consider a fi ctional dedicated music player device for sporty users. The device is strictly