National Bibliography Numbers, NBNs, are used by the national
libraries and other organizations in order to identify various
resources such as digitized monographs. Generally, NBNs are applied
to resources that do not have an established (standard) identifier
system of their own.
A URN (Uniform Resource Names) namespace for NBNs was established in
2001 in RFC 3188. Since then, several European national libraries
have implemented URN:NBN-based systems.
This document replaces RFC 3188 and defines how NBNs can be supported
within the updated URN framework. A revised namespace registration
(version 4) compliant to the RFC 3406bis draft is included.