104 Personal Content Experience: Managing Digital Life in the Mobile Age 33 initiatives based on XMP, such as Creative Commons, IPTC, and W3C to name but few (Rosenblatt 2002). XMP is not tied to single content type, and is built on open W3C standards: it is an implementation of RDF (Section 5.7.3). Furthermore, XMP is extendable, also by third parties. It is especially targeted at creative professionals. XMP consists of four building blocks: 1. XMP Framework: RDF Framework for expressing metadata from multiple schemas; 2. XMP schemas: Schemas used to describe properties, contained in namespaces; 3. XMP Packet Technology: Method for embedding XML fragments in binary streams; 4. XMP SDK: Support for third party interface and extensions to XMP. Of the existing metadata content standards to date, XMP appears to have the most fl exible design, in terms of extensibility and application interfacing, while tying to the (potentially huge) RDF-based information sources in the Semantic Web. XMP has also subsumed an earlier de facto standard, “IPTC Headers” that Adobe adopted in their Photoshop image manipulation software, particularly used in professional digital photography. The headers embed metadata into image fi les in JPEG, TIFF, and Photoshop formats. Other vendors have also adopted the use of these metadata fi elds in their image editors. The key use of the metadata structures is multi- media news exchange between professional news agencies and pub- lishers, which is refl ected in the choice of the metadata attributes. The IPTC headers are based on an Information Interchange Model 34 (IIM) that was designed for universal data transfer of graphical, textual, or other multimedia information. It is structured as an envelope around a data object, or collection of objects. This general format allows encapsulation of any metadata with any objects; however, the main use to date has been in the professional news domain. Besides generic metadata initiatives, there are several metadata formats that are more or less tied to specifi c content types. The best- known for general public are undoubtedly MPEG-1 Layer 3 audio media type with its embedded ID3v2 tag information (such as song 33 http://www.adobe.com/products/xmp/standards.html 34 http://www.iptc.org/IIM/