Chapter 4: Metadata Magic 111 content that can be easily summarized due to its hierarchical structure. The metadata fi elds defi ned by RSS have already been used for a number of purposes beyond news summaries, for instance stock charts, book reviews, comics, price trackers, classifi ed ads, and others. This relatively lightweight metadata standard has arguably allowed a surge in the machine-readable Web content – including personal content. 4.6.10 Summary Unfortunately, the fi eld of multimedia metadata standards is unclear and immature at best. The sheer number of different media formats alone makes it a real challenge, not to speak of the huge data volume and the number of practitioners in the fi eld, and the number of fi elds. Adoption to different proposals has been slow, and vendors provide their proprietary, application-specifi c solutions. It is evident that no single body can take care of all metadata standardization efforts: the domain is simply too wide (Smith and Schirling 2006). This calls for better co-operation between the standardization bodies and an adoption of a more modular approach. 4.7 The PCE Trinity: Mobility, Context, and Metadata The discussions above reveal a signifi cant fact: the existing metadata formats and standards do not consider consumer use by design. Some of them can be applied to personal use, yet inherently they are all targeted at content creation professionals. What, then, would be needed in such a metadata standard? As we emphasized in section 4.4, the importance of people, that is, social relationships, is a key issue. Here, we will discuss another aspect, inher- ent in mobile use: context-awareness – the capacity of the devices to take into account the user’s situation. These two aspects are mostly missing in existing metadata standards. Mobility from the device perspective refers to something that is capable of being moved. This is a fundamental characteristic of a mobile device, since it distinguishes them from desktop computers. From the user’s point of view, in section 2.2 we categorized mobile device use as continuous or nomadic, depending on if the device can be operated at the same time as the user is moving (for instance, by foot or driving a car). To emphasize, truly mobile devices for continuous use are the ones that the user can use even while on the move.