MADS 2.0 is now out. This is the first major revision of the Metadata Authority and Description Schema since 2005.
Major changes, according to the Library of Congress, include elimination of dependence on the MODS schema, updated elements that are the same in MODS to reflect version 3, addition of authority URI and value URI for controlled lists, addition of classification and language elements, and ability to specify if a subject heading can be subdivided geographically.
Mad File Format Science 