URN , or Uniform Resource Name, is an IETF RFC specifies a syntax for URIs that server as persistent location-independent resource identifiers.
A URN is a URI which names a resource. URLs, in contrast, describe the location of a resource. RFC 2141 has the URN of urn:ietf:RFC:2141, and the URL http://www.ietf.org/rfc2141.txt .
Given the serverity of this situation, I wonder why URNs have never caught on?