Abstract: This document lays out general definitions of and mechanisms for establishing Uniform Resource Names (URN) "namespaces".The URN WG has defined a syntax for URNs in RFC 2141, as well as some proposed mechanisms for their resolution and use in Internet applications in RFC 3401 and RFC 3405.The whole rests on the concept of individual "namespaces" within the URN structure.Apart from proof-of-concept namespaces, the use of existing identifiers in URNs has been discussed in RFC 2288.