206 Personal Content Experience: Managing Digital Life in the Mobile Age Participatory design takes the actual users along various design phases. Since the designer is rarely the user (or vice versa), it is con- sidered benefi cial to include actual users in the design process in order to exploit their domain expertise. Iterative design and (rapid) prototyping refer to creating interactive demonstrations at a fast pace to test different concepts. Based on usability evaluations, the demonstrations may be iterated further or in some cases discarded (validating the design and usability engineering will be introduced in section 6.3). The benefi t of this approach is that it enables swift testing of different kinds of design solutions, even if all the other parts of the system are not yet ready. Potentially the proto- types reveal, in early design stages, usability problems that could poten- tially have a negative impact on the fi nal product. Furthermore, high fi delity prototypes give tangible demonstrations on the concepts to various stakeholders, for instance, management, marketing, and cus- tomers, which aid communication between the people involved. In addition to UI designers and possible users, the design process should involve many other people, such as graphic designers, hardware and software developers, technical writers, and managers, to assure that the design is valid and feasible. 6.2 Interacting with Mobile Personal Content Besides understanding the general characteristics of people, when designing user interfaces for mobile media, it is equally important to examine the ways they interact with content. As far as digital personal content is concerned, the changes in behavioural patterns signifi cantly affect the interaction. In this section, we will look at interactions that are typical with the most prominent forms of personal content – photos, music, and video.2 For changes in interaction, mobility is the key factor: timely infor- mation, instant sharing, and spontaneous use patterns are direct consequences of mobile access to personal content. Mobile devices, especially those used for personal communications, are among the most trusted digital devices consumers have ever experienced. This is not because of their technical superiority over other digital devices, 2 The fi ndings presented in this section, relating to user experience and users’ behav- ioural habits with photos, music, and video, are gained in several internal studies over the last six years. So far, the studies have been conveyed in Nokia internal technical reports only, and the results are now publicly available for the fi rst time.