- Elizabeth Rogers
Metadata Encoding & Transmission Standard – History
The origins of the Metadata Encoding & Transmission Standard, or METS, can be traced back to a 1996 attempt by The University of California Berkley to address the institution’s inability to rebind pages of a book once they had been digitized. The program created by UC Berkley, called Ebind, was not successful. However, it paved the way for another attempt at solving this problem, the “Making of America II Project”. This project, started in 1998, was taken on by several U.S. universities, including UC Berkley (McDonough, 2005). While MOA2 was a step in the right direction towards the organization of digital objects, it was discovered that MOA2 had limited ability to fulfill this role. In 2001, a group of libraries working on digital library development programs decided that a replacement for MOA2 was needed, which led to the development of METS (McDonough, 2005).
Metadata Encoding & Transmission Standard – Importance and Significance
When an institution creates metadata for a resource, particularly a book, the metadata can be used to aide users in finding the book, and helps the library keep an accurate account of its collection and holdings. However, if the library fails to create accurate structural metadata, that does not mean the resource is lost or that the pages of the book will be forever separated. The same cannot be said of books once they are digitized. When a book is digitized, each page becomes a separate resource, and before the creation of METS, there was no encoding standard that provided a platform to create the structural metadata necessary to digitally “bind” these resources to ensure that they would be findable and able to used and evaluated as a cohesive unit (“METS: An Overview & Tutorial”, 2016). Brad Westbrook, a librarian at the University of California in San Diego, describes METS as “an XML standard that is a type of digital wrapper. It functions to relate the components of a digital resource” (Rose, 2005). METS was specifically created for the digital library community to allow for the digitization and encoding of complex digital objects, like books or presentations. These resources can contain a variety of parts as well as different types of files. For example, one presentation can contain text files, images, video, and sound files. Using the structural metadata elements included in METS, institutions can ensure that all components of a resource are linked, even if they are stored in different places. METS also enables institutions to use structural metadata to control the presentation of resources and ensure that the objects are presented in the way they were intended to be (Rose, 2005).
As previously stated, METS was born out of MOA2. METS did not replace MOA2, but rather built upon the work that had already been done. One of the major shortcomings of MOA2 was its lack of flexibility at the local level with administrative and descriptive metadata elements. METS allows for flexibility at the local level with administrative and descriptive metadata, as it does not require either of these to be included in an object’s METS document. If descriptive or administrative metadata are used, METS does not require the use of controlled vocabularies for many elements, and allows for the use of whatever metadata element set the record creator chooses, furthering its increased flexibility over MOA2 (McDonough, 2005). Additionally, MOA2 was limited by its ability to encode only texts and still image media. MOA2 was unable to encode audio or video resources. Even in 2001, this would pose a significant challenge to any library with a well-developed collection that was serious about digitizing all of its resources (McDonough, 2005). METS gives institutions and repositories the ability to encode audio and video resources, in addition to print objects. Finally, METS was created to allow for improved sharing of digital objects between repositories, which MOA2 could not facilitate (McDonough, 2005).
Metadata Encoding & Transmission Standard – Schema Description
METS documents are created using XML, so that the document is machine readable. A METS document can include up to seven sections, METS header, descriptive metadata, administrative metadata, file inventory, structural map, structural links, and a behaviors section. The only required, and most important, section for a METS document is the structural map. The structural map defines a hierarchical structure for a digital object, this section is where the relationship between the digital object’s files is described. The information found in this section is what allows users to more easily look through a digital object, much in the way a user would look through a physical book. The structural map can also links the object’s digital files back to their descriptive and administrative metadata (McDonough, 2005). The structural map is a unique aspect of this scheme because it can be represented by an actual diagram that illustrates the relationships between the parts of an object and the objects metadata.
Another unique section of the METS document is the structural links section. This section is generally used in the archiving of websites. It allows the document creator to record hyperlinks between items in the structural map. A METS structural map can show the page hierarchy of a website, showing the relationship between a “parent” page and subsequent “child” pages underneath it. The structural links section allows for the recording of links between the “child” pages that would not be displayed in a traditional hierarchical organizational structure (“METS: An Overview & Tutorial”, 2016). The behaviors section of a METS document is used to record behavioral metadata. This section records any metadata related to software or applications that may be needed to view, or use, a digital object. The behaviors section enables institutions to exercise control over how users experience a digital object. However, this section can also create significant challenges for repositories. Software and applications change consistently and often, rapidly. If a behavior changes, a repository manager would need to modify the record for every object associated with this behavior (McDonough, 2005).
The seven required sections of a METS document are also some of the top level elements used in METS. Other elements unique to METS include, structural requirements, technical requirements, maintenance agency, behavior files, and description rules. This is a departure from other schemas that tend to include top level elements that lend themselves solely towards descriptive metadata. In METS, these traditional descriptive elements are found within the descriptive metadata element. Here, elements from Dublin Core, MARC, MODS, EAD and VRA can be wrapped inside METS sub elements to describe the digital work (“METS: An Overview & Tutorial”, 2016). This distinction is important because it reinforces that while METS does allow for the inclusion of descriptive metadata, its focus is on the administrative and structural metadata that is necessary to maintain the object’s original structure and presentation.
Metadata Encoding & Transmission Standard – Resources
METS Schema & Documentation. (2016, August 9). Retrieved March 12, 2017, from http://www.loc.gov/standards/mets/mets-schemadocs.html
Schema Documentation. (2011, July 1). Retrieved March 12, 2017, from https://www.loc.gov/standards/mets/profile_docs/mets.profile.v1-2.html
METS: An Overview & Tutorial. (2016, February 9). Retrieved March 12, 2017, from https://www.loc.gov/standards/mets/METSOverview.v2.html#structlink
Rose, Trish. (Summer 2005). METS: A Data Standard for Access and Preservation Now and Into the Future. Digital Letters, 8, 1-4.
McDonough, Jerome. (2006, February 1). METS: standardized encoding for digital library objects. International Journal on Digital Libraries, 148-158.