196 Personal Content Experience: Managing Digital Life in the Mobile Age for ensuring application interoperability, but still support easy and fl ex- ible end user metadata tagging. We also discussed how it is important to create future-proof ontologies, since we cannot know all possible metadata needs now. There will always be many content types in use and new ones will be invented to solve yet unknown needs. However, we cannot create yet another metadata format but our metadata model must work with all current and future formats. Thus, we only created an internal API that applications can use, not the format itself. We incorporated harvesters into our metadata model to convert metadata from existing formats into our internal format, and vice versa. Finally, we described our prototype framework that we have imple- mented on Symbian S60 devices. We went through its components and their functions and also how it is intended to be used. 5.11 References Adjeroh D.A. and Nwosu K.C. (1997) Multimedia Database Management – Requirements and Issues, IEEE MultiMedia, Volume 4, Number 3, pp. 24–33, July 1997. Berners-Lee T., Hendler J., and Lassila O. (2001). The Semantic Web. Scientifi c American Volume 284, Number 5, pp. 34–43. Available online at: http://www.sciam.com/article.cfm?articleID=00048144-10D2-1C70- 84A9809EC588EF21. Bernstein P.A., Hadzilacos V., and Goodman N. (1987) Concurrency control and recovery in database systems. Addison-Wesley Longman Publishing Co., Inc. Boston, MA, USA. Boiko B. (2005) Content Management Bible (2nd edn.). Wiley Publishing, Inc. Indianapolis, IN, USA. Dingledine R., Freedman M.J., and Molnar D. (2001) Free Haven. In: Oram A. (ed.) Peer-to-peer: Harnessing the Power of Disruptive Technologies. O’Reilly & Associates, USA, pp. 159–187. Hirata K. and Kato T. (1992) Query by Visual Example – Content based Image Retrieval. Proceedings of the 3rd International Conference on Extending Database Technology: Advances in Database Technology table of contents, pp. 56–71, Springer-Verlag, London, UK. Katz R.H. (2002) Adaptation and mobility in wireless information systems. IEEE Communications Magazine, May 2002, Volume 40, Issue 5, pp. 102–114. Lin F. (2002) Multimedia and multi-stream synchronization. In Distributed multimedia databases: techniques & applications, pp. 246–261, Idea Group Publishing, Hershey, PA, USA. Marpe D., Wiegand T., and Sullivan G.J. (2006) The H.264 / MPEG4 Advanced Video Coding Standard and its Applications, IEEE Communications Maga- zine, Volume 44, Number 8, pp. 134–144, August 2006.