METS, which stands for Metadata Encoding and Transmission Standard, is a data communication standard used for digital collections in cultural heritage institutions, including libraries, archives, and museums (Cantara, 2005; Cundiff, 2004; Digital Library Foundation, 2010; Elings & Waibel, 2007; Guenther & McCallum, 2003, Maze, 2012; NISO, 2004). The METS schema is an open standard used for both storing and transmitting data for digital resources. It was developed by the Digital Library Foundation a little over ten years ago, and is currently maintained by the Library of Congress (Library of Congress, 2012, METS Web Site). METS is often used to encode metadata for digital audio, digital video, or digital images. This paper will first provide a brief description of METS as a wrapper with external metadata schemas. The literature review section will then focus on METS' development since 2001, its recent uses with external schemas such as MODS and PREMIS, and its use with digital audio and visual metadata records.
METS and External Schemas
A METS record is comprised of a wrapper. The wrapper begins and ends with METS tags, and surrounds the external schema with which it is used. The METS wrapper has a basic structure, with up to seven major subsections: a METS Header (metsHDR), a Descriptive Metadata Section (dmdSec), an Administrative Metadata Section (amdSec), a File Section (fileSec), a Structural Map (structMap), Structural Links (structLink), and a Behavior Section (behaviorSec). The METS document must have at minimum the Structural Map (Cundiff, 2004; Digital Library Foundation, 2010). Each of these subsections has elements that provide the means for describing in detail the digital objects. The Structure Map or Structural Map defines a hierarchical structure so users of the digital library object can navigate through it via METS pointers (LC, 2011, METS: An Overview and Tutorial).
"External schemas are schemas that define an XML vocabulary and syntax appropriate for use in conjunction with METS in its descriptive and administrative metadata contexts" (Library of Congress, 2011, METS Extenders). METS is displayed using XML (Extensible Markup Language), and it is especially useful as a wrapper with MODS (Metadata Object Description Schema), Dublin Core, and PREMIS (Preservation Metadata: Implementation Strategies). MODS and Dublin Core are descriptive metadata schemas used for identifying digital resources, and PREMIS is an administrative metadata schema used for the preservation of digital resources (Bolin, February 2013).
METS Literature Review
Library of Congress METS Web Site
The intended audience for METS is generally the cultural heritage community, including digital collections in libraries, archives, and museums. Since the METS standard is maintained in the Network Development and MARC Standards Office of the Library of Congress, the Library of Congress METS web site is an invaluable resource for digital libraries and collections with digital objects. The METS web site offers an abundance of resources, which are well organized and easy to navigate, including a basic introductory article (Library of Congress, 2011, METS: An Overview and Tutorial).
According to the Library of Congress (2012, METS Web Site), "The METS schema is a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, expressed using the XML schema language of the World Wide Web Consortium." The Library of Congress offers information on external schemas that can be used with METS. The following descriptive metadata schemas have been endorsed by the METS Editorial Board for use with METS: Dublin Core, MODS, MARCXML, and VRA Core. METS has also been endorsed for use with the following administrative metadata schemas: textMD (Schema for Technical Metadata for Text), and MIX (NISO Technical Metadata for Digital Still Images). There are also specific audio and video metadata schemas that are compatible with METS, including audioMD and videoMD. Finally, METS is endorsed for use with PREMIS for preservation metadata.
The Library of Congress provides tools on integrating these schemas, and these tools support external metadata creation for use with METS (Library of Congress, 2012, METS Tools and Utilities). The Library of Congress' METS web site also includes links to examples of METS documents for the following: bibliographic records, page turners, maps, various types of images, PDFs, sheet music and scores, sound recordings, realia, serials, and video (Library of Congress, 2011, Example Documents). Overall, the Library of Congress METS web site is an important resource for those seeking information on METS.
What does scholarly and professional literature say about METS' development since 2001 for the cultural heritage community, including its uses with audio and visual resources? There is not an abundance of literature available on METS, since it is a relatively recent...