METS: Overview and Tutorial

Library of Congress, Network Development and MARC Standards Office. METS: An Overview and Tutorial. Washington, DC: Library of Congress, 2004. Last updated September 23, 2004. Available online at http://www.loc.gov/standards/mets/METSOverview.v2.html (accessed 17 April 2005).

The METS overview and tutorial on Library of Congress’s Metacoding Encoding & Transmission Standard website touches on basic principles and aspects of this metadata schema. Developed by the Library of Congress as initiative of their Digital Library Federation, and maintained by the Network Development and MARC Standards Office of the Library of Congress, METS is meant to be a structural system for maintaining the integrity of digital libraries and their objects. Unlike metadata for traditional library items, like books, digital files require information infrastructures to maintain their connections with other files and webpages—a challenge that is complicated even more with the challenge of long-term digital preservation with its requirements for refreshment and migration of file formats. The structural map—embedded within a METS file—provides the basic framework by which digital objects maintain their links to related objects and files, and provide descriptive and administrative metadata about the object itself.

This initiative was created as a means to turn digital library objects into long-term archival information packages, housed in digital mass storage systems. It can play an integral part of Open Archival Information Systems. There are seven major components of a METS document: METS header (which contains metadata about the METS document), descriptive metadata (bibliographic information housed inside or external to the document itself), administrative metadata (how the files were created and stored, along with rights information), file section (which provides for object versions), structural map (which provides a hierarchy and links objects to their metadata), structural links (which records hyperlinks between nodes) and behavior (of executables). Expressed in XML, it is hoped that this schema is extensible and interoperable enough to provide long-term information about the objects in digital libraries.