Started in 2011, BIBFRAME, short for Bibliographic Framework, is an RDF vocabulary and associated technologies that is sponsored by the Library of Congress as an eventual replacement for MARC21. The current version (1.0) of BIBFRAME is made up four main classes; Works, Instances, Authorities, and Annotations. The following graphic from the bibframe.org shows the relationships between these classes as a model for describing bibliographic resources and their relationships.
Source http://bibframe.org/static/images/bibframe.png"