Chapter 5: Realizing a Metadata Framework 129 is suffi cient to know that ontology is basically a list of items and their relationships that our framework knows to exist. It will be discussed in more detail in section 5.6. For the purposes of providing the applications with access to content, context, and metadata, we have designed and implemented a personal content framework. The developed framework acts as a real-world case study, showing how to deal practically with the issues related to content management, and how the application development is affected. The framework provides all application developers with a good, strong, and level scaffolding on which to build robust applications using meta- data, and offers a unifi ed way of storing and managing metadata regardless of its type or origin. Furthermore, it allows developers to focus on how to leverage metadata for creating better applications, instead of having to deal with low-level metadata management issues. As discussed throughout this book, the importance of metadata increases along with the amount and variety of content objects. As pointed out in Chapter 2, even mobile devices with a limited storage capacity are equipped with gigabytes of cheap storage space, and the amount of fi les is close to that found on PCs a decade ago. For example, as recently as 2006, a 1 GB memory card was the norm for storage in mobile devices, and 2 GB cards are now available and not much more expensive. This means that the amount of available storage memory in mobile devices will continue to increase rapidly. At the same time, mobile devices have expanded from mere “E” devices into “GE”. You can shoot photos and videos, record audio, create multi- media presentations, and so on. A mobile device can also connect to your home network and access all content you have on your media servers and in other devices in the personal content device ecosystem. Finally, the connectivity allows easy and instant sharing. All the facts described above add to the number of accessible content objects from within a mobile device. As a consequence, tra- ditional directory or folder hierarchies are not adequate for maintaining or even fi nding your own content (section 3.3). Then metadata becomes a key element in all aspects of content management and so also needs to be managed. From a personal content software point of view, there are two primary options for metadata management. Either each application takes care of its own metadata by using its own designs and methods, or the operating system (OS) provides a system-wide metadata manage- ment service that takes care of metadata for all applications. Both approaches have their pros and cons. Since we emphasize the impor- tance of metadata in all content management tasks, we choose the latter