Mariela Hristova's Assignment 5


Compare and contrast Dublin Core, METS, and MPEG-21.


Even though Dublin Core, METS (Metadata Encoding and Transmission Standard) and MPEG-21 (Moving Picture Experts Group) are all metadata standards, each one of them offers unique functionality because of the specific goals with which it was designed.

Dublin Core sets out to establish a minimum threshold of metadata fields for a non-specialist to use in describing electronic materials (it could be used for other types of materials, but is most suitable for electronic ones). The standard deals primarily with descriptive/bibliographic metadata and has 15 core fields, the definition of which is somewhat open to interpretation by the person applying the standard. In a sense, Dublin Core is simple and brief enough to invite non-specialists into the habit of generating metadata for electronic documents as they create the documents themselves, but its simplicity and flexibility can be seen as limitations. Dublin Core's potential in contributing to high interoperability is limited exactly because of the lack of strict definitions, vocabulary control or authority files. The focus on descriptive metadata to the exclusion of other types can be another potential limitation of the standard in comparison to METS and MPEG-21. Still, one should not fail to acknowledge that Dublin Core takes us beyond the MARC format traditionally used within the context of libraries.

METS is another metadata standard that has a particular, and very different, goal. It does not focus so much on the semantic aspect of guiding the generation of metadata, but on the transmission of already generated/extracted metadata. METS is a standard for encoding in XML format that can be used once a specific other standard has already governed the generation of the metadata. METS is a de facto standardized container for metadata. This unique functionality can facilitate interoperability by providing a standard format through the use of XML for sharing metadata across digital collections. Its exclusive focus on the encoding, however, retains the need for crosswalks because the actual metadata can be compliant with a number of different standards, i.e. METS can enable sharing of metadata, but cannot eliminate the need for translation.

By comparison to the previous two, MPEG-21 is a standard with much more ambitious goals, which takes an object-oriented approach to materials, since it concentrates on metadata for multimedia resources. It seems to be trying to enable interoperability by supporting more than just the kind of descriptive metadata that Dublin Core supports, and by creating a file format that carries both an object and its metadata in a standardized manner, going beyond METS' use of XML. Needless to say, such an ambitious goal necessarily results in a complex standard. MPEG-21 includes a variety of components, such as Digital Item Declaration and Identification, Intellectual Property Management and Protection, Rights Expression Language, Rights Data Dictionary, Digital Item Adaptation, and File Format. Each of those components in its turn provides rules and guidelines for dealing with a specific type of metadata or aspect of the metadata generation process. As a result, MPEG-21 regulates both the generation of metadata and its encoding into a file format.



The Library of Congress. (2003). METS: An Overview and Tutorial. Metadata Encoding and Transmission Standard (METS). Retrieved July 20, 2004 from

MPEG-21 Overview v.5. (2002). Internation Organization for Standardization. Retrieved July 20, 2004 from

Using Dublin Core. (2003). Dublin Core Metadata Initiative. Retrieved July 20, 2004 from