The MPEG-21 rights expression language and rights data dictionary

The MPEG-21 Rights Expression Language (REL) is an XML-based language for digital rights management (DRM), providing a universal method for specifying rights and conditions associated with the distribution and use of assets like content, resources and services. Evolved from the eXtensible rights Markup language (XrML), the REL facilitates the creation of an open DRM architecture for managing and protecting these assets. As a general-purpose rights expression language, the REL is agnostic to types of assets, platforms and media, and expressive enough to support applications that can be even beyond DRM, including protecting privacy. It also contains additional capabilities in the areas of extensibility, security, trust management, and life cycle management of rights. This article provides an overview of the REL in terms of its data model, expressiveness, authorization model, structure for extensibility and profiling, and usages in digital media, trust management, and web services. To support the REL and provide extensive semantics for the management of rights, MPEG-21 also defined a Rights Data Dictionary (RDD). Based on original work conducted by , the MPEG-21 RDD specifies a methodology and structure for the RDD dictionary. The specification defines a core set of terms and provides a mechanism for the introduction of further terms through a registration authority. The RDD also supports the mapping of terms from different namespaces.