The developers of the Metadata Encoding and Transmission Standard (METS) recently announced a revised METS XML schema. The METS Schema is "a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, expressed using the W3C XML schema language." Originally developed as as an initiative of the Digital Library Federation, METS is maintained by the US Network Development and MARC Standards Office of the Library of Congress, with development coordination through the Research Libraries Group (RLG). METS provides "an XML encoding format for digital library objects that was designed for application as a Submission Information Package (SIP), Dissemination Information Package (DIP) and Archival Information package (AIP) within the Open Archival Information System reference model." METS has been implemented in several digital library projects (e.g., National Gallery of the Spoken Word; the METAe project, UCBerkekey, California Digital Library, LOC Audio-Visual Prototyping Project), and has been identified in the Submission Information Package (SIP) Specification recently published by the Harvard University E-Journal Archive project. The revised METS XML schema makes a number of changes and enhancements, and now requires the use of an additional XML schema document defining XLink attributes.

METS document summary from the Version 1.0 epsilon XML Schema documentation: "METS is intended to provide a standardized XML format for transmission of complex digital library objects between systems. As such, it can be seen as filling a role similar to that defined for the Submission Information Package (SIP), Archival Information Package (AIP) and Dissemination Information Package (DIP) in the Reference Model for an Open Archival Information System. A METS document consists of five possible subsidiary sections: metsHdr (METS document header), dmdSec (descriptive metadata section), amdSec (administrative metadata section), fileGrp (file inventory group), and structMap (structural map). It also has five possible attributes: [1] ID: (an XML ID); [2] OBJID: a primary identifier assigned to the original source document; [3] LABEL: a title/text string identifying the document for users; [4] TYPE: a type for the object, e.g., book, journal, stereograph, etc.; [5] PROFILE: the registered profile to which this METS document conforms."