This schema is currently referred to as "NISO Metadata for Images in XML (NISO MIX)". MIX is expressed using the XML schema language of the World Wide Web Consortium. MIX is maintained for NISO by the Network Development and MARC Standards Office of the Library of Congress with input from users.
The DjVuLibre XML Tools provide for editing the metadata, hyperlinks and hidden text associated with DjVu files. Unlike djvused(1) the DjVuLibre XML Tools rely on the XML technology and can take advantage of XML editors and verifiers.