The concept of abstract types is indicated by xsi:type and is used in MPEG-7 and MPEG-21
a policy to manage digital rights expressed by MPEG-21
Rights Expression Language (REL)  profiles that enables the governed sharing of digital items along with the protection of the intellectual property, a secure structured overlay network that assures the basic security functionalities providing an effective defense against well known attacks,
Lambert continues, "Another significant obstacle to the adoption of XrML (and ISO MPEG-21
REL) is the claim by ContentGuard that XrML in particular, and any REL in general, are covered by ContentGuard patents.
This paper proposes a hierarchical learning design framework based on the MPEG-21
The MPEG-7 and MPEG-21
standards have been developed to support such requirements.
Without doubt, the most complete initiative trying to identify and represent the context for generic multimedia applications has been carried out by the MPEG community by means of the 7th part of its MPEG-21
Rosenblatt acknowledges, I pointed out in the article that RealNetworks withdrew sup port from XMCL during the MPEG-21
competition for Rights Expression Languages in December 2001.
As MPEG-7 and MPEG-21
are the dominant standards for multimedia application support, the research in this area is mainly based on them.
Coverage includes the fundamentals of digital video compression, digital video coding standards, transcoding algorithms and systems architecture, optimization of transcoding performance, video transport transcoding, system clock recovering and time stamping, transcoder video buffer and hypothetical reference decoder, cryptography and conditional access, application and implementation of transcoding, universal multimedia access with emerging standard MPEG-21
, and the end-to-end test bed.