It is a source of precise semantics which can be used to describe both the types of permissions owners may wish to grant to users and the context within which the permissions apply. The MPEG-21 Rights Data Dictionary specification does two things. Firstly it describes a methodology for creating a structured dictionary of clear, consistent, integrated and uniquely identified terms for the purposes of rights management. Secondly, it supports the MPEG-21 Rights Expression Language and specifies how further Terms may be defined under the governance of a Registration Authority, requirements for which are described in Annex C of the specification.