About the MPEG-21 Standard (ISO/IEC 21000)
MPEG-21 (ISO/IEC 21000) is a multimedia framework to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities.
The core of MPEG-21 is the Digital Item, which is the digital representation of "a work", and as such is the thing that is acted upon (managed, described, exchanged, collected, etc.) within the model. The goal of this model is to be as flexible and general as possible, while providing for the "hooks" that enable higher level functionality. This, in turn, will allow the model to serve as a key foundation in the building of higher level models in other MPEG-21 elements such as Identification & Description or Intellectual Property Management & Protection (IPMP, MPEG's term for Digital Rights Management).
IPMP relies on a Rights Expression Language (defined in ISO/IEC 21000-5) which, in turn, use the RDD to provide semantics for the terms used in Rights Expressions. ISO/IEC 21000-6 defines the methodology of how to define and create these terms.
For more information, please visit the homepage of ISO/IEC JTC 1/SC 29/WG 11 (MPEG), the body that developed and maintains the MPEG-21 standards where there is also further information on MPEG-21.