MODS was created by the Library of Congress’ Network Development and MARC Standards Office together with other interested experts as a multi-function bibliographic element set schema with particular value for library applications.

As an XML schema MODS is intended to be able to carry selected data from existing MARC21 records as well as to enable the creation of original resource description records. It includes a subset of MARC fields and uses language-based tags rather than numeric ones, in some cases regrouping elements from the MARC21 bibliographic format.

MODS is expressed using the XML schema language of the World Wide Web Consortium. The standard is maintained by the Network Development and MARC Standards Office of the Library of Congress with input from users.