The ISO/IEC 21000 (MPEG-21) series of International Standards defines an open framework for multimedia delivery and consumption, with both the content creator and content consumer as focal points. The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities.
This second part of MPEG-21 (ISO/IEC 21000-2:2005) specifies a uniform and flexible abstraction and interoperable representation for declaring the structure and makeup of Digital Items. A Digital Item Declaration (DID) involves specifying the resources, metadata, and their interrelationships for a Digital Item. A DID is done using the Digital Item Declaration Language (DIDL).