2. Requirements for functional capabilities

These are the requirements for URNs' functional capabilities:

• Global scope: A URN is a name with global scope which does not imply a location. It has the same meaning everywhere.

• Global uniqueness: The same URN will never be assigned to two different resources.

• Persistence: It is intended that the lifetime of a URN be permanent. That is, the URN will be globally unique forever, and may well be used as a reference to a resource well beyond the lifetime of the resource it identifies or of any naming authority involved in the assignment of its name.

• Scalability: URNs can be assigned to any resource that might conceivably be available on the network, for hundreds of years.

• Legacy support: The scheme must permit the support of existing legacy naming systems, insofar as they satisfy the other requirements described here. For example, ISBN numbers, ISO public identifiers, and UPC product codes seem to satisfy the functional requirements, and allow an embedding that satisfies the syntactic requirements described here.

• Extensibility: Any scheme for URNs must permit future extensions to the scheme.

• Independence: It is solely the responsibility of a name issuing authority to determine the conditions under which it will issue a name.

• Resolution: A URN will not impede resolution (translation into a URL, q.v.). To be more specific, for URNs that have corresponding URLs, there must be some feasible mechanism to translate a URN to a URL.