ISO/IEC 21000-6:2004描述了一个版权数据字典，其中包括一组清晰、一致、结构化、集成和唯一标识的术语，以支持MPEG-21版权表达语言（REL），ISO/IEC 21000-5。附录A规定了RDD词典的方法和结构，并规定了在注册机构的管理下如何定义更多术语，其要求见附录C。 这些规范以及RDD字典和数据库共同构成了RDD系统。使用RDD系统将有助于参与数字项目权利管理和使用的相关方之间准确交换和处理信息，尤其是支持ISO/IEC 21000- 5（REL）。第6条描述了ISO/IEC 21000-6:2004与ISO/IEC 21000-5的关系。 除了提供ISO/IEC 21000-5中使用的术语定义外，RDD系统还旨在支持不同名称空间中术语的映射。这种映射将使元数据能够从一个名称空间（或机构）的术语转换为另一个名称空间的术语。映射是注册机构的责任，以确保将歧义或语义完整性损失降至最低。提供自动trm查找也是一项要求。 RDD词典是一个规定性词典，它定义了一个特定RDD授权术语名称所代表的trm的单一含义，但它也具有包容性，因为它可以识别其他权威机构对其他标题词和定义的规定，并通过映射将其合并。 RDD字典还支持相同的名称在不同的权限下可能具有不同含义的情况。ISO/IEC 21000-6:2004描述了审计规定，以便跟踪术语及其属性的添加、修改和删除。 ISO/IEC 21000-6:2004将法律定义视为且仅视为可映射到RDD字典中的来自其他机构的术语。因此，RDD注册机构直接授权的条款既不定义也不规定知识产权或其他法律实体。

ISO/IEC 21000-6:2004 describes a Rights Data Dictionary which comprises a set of clear, consistent, structured, integrated and uniquely identified terms to support the MPEG-21 Rights Expression Language (REL), ISO/IEC 21000-5. Annex A specifies the methodology for and structure of the RDD Dictionary, and specifies how further Terms may be defined under the governance of a Registration Authority, requirements for which are described in Annex C. Taken together, these specifications and the RDD Dictionary and Database make up the RDD System. Use of the RDD System will facilitate the accurate exchange and processing of information between interested parties involved in the administration of rights in, and use of, Digital Items, and in particular it is intended to support ISO/IEC 21000-5 (REL). Clause 6 describes how ISO/IEC 21000-6:2004 relates to ISO/IEC 21000-5. As well as providing definitions of terms for use in ISO/IEC 21000-5, the RDD System is designed to support the mapping of terms from different namespaces. Such mapping will enable the transformation of metadata from the terminology of one namespace (or Authority) into that of another namespace. Mapping, to ensure minimum ambiguity or loss of semantic integrity, will be the responsibility of the Registration Authority. Provision of automated trm look-up is also a requirement. The RDD Dictionary is a prescriptive dctionary, in the sense that it defines a single meaning for a trm represented by a particular RddAuthorized TermName, but it is also inclusive in that it can recognize the prescription of other Headwords and definitions by other Authorities and incorporates them through mappings. The RDD Dictionary also supports the circumstance that the same name may have different meanings under different Authorities. ISO/IEC 21000-6:2004describes audit provisions so that additions, amendments and deletions to Terms and their attributes can be tracked. ISO/IEC 21000-6:2004 recognizes legal definitions as and only as Terms from other Authorities that can be mapped into the RDD Dictionary. Therefore Terms that are directly authorized by the RDD Registration Authority neither define nor prescribe intellectual property rights or other legal entities.