The Metadata Encoding and Transmission Standard (METS) is an open standard which uses an XML Schema (XSD) for structural metadata description and administration of digital objects such as images, text, audio, video, etc. There are digital objects that consist of two or more other individual digital objects, such as a book with multiple image files. METS can be used for encoding descriptive, administrative, and structural metadata.

A METS document may include seven sections:

• METS Header(<metsHdr>)

  The METS Header is modeled after the Text Encoding Initiative (TEI) Header and describes the metadata of the METS document.

• Descriptive Metadata Section (<dmdSec>)

  This section includes descriptive information about the digital object such as its discovery and identification. It can include elements such as title, abstract, author, keywords, etc.

• Administrative Metadata Section (<amdSec>)

  The section provides administrative information to the digital object such as when and how it was created and stored, file type, its property rights and licensing information, etc.

• File Group Section (<fileSec>)

  The File Section specifies all the files belong to the object.

• Structural Map (<structMap>)

  The section describes the hierarchical structure of the original digital object.

• Structural Map Linking Section (<structLink>)

  The Structural Map Linking Section describes the documentation of hyperlinks between two divisions in the Structural Map section and was designed primarily to save the hyperlinks in archived Web sites.

• Behavior Section (<behaviorSec>)

  The last section provides information about executable codes associated with the content of the digital library object.

From all above listed METS sections, only the Structural Map is required and other sections are optional.

The format of metadata in several sections is not specified and can be varied, for example Dublin Core can be used for the descriptive metadata section, and the NISO image technical metadata for the administrative metadata section. These properties shows that METS is extensible and modular.