URI Resolution Services Necessary for URN Resolution

Retrieving the resource identified by a Uniform Resource Identifier (URI) [3] is only one of the operations that can be performed on a URI. One might also ask for and get a list of other identifiers that are aliases for the original URI or a bibliographic description of the resource the URI denotes, for example. This applies to both Uniform Resource Names (URNs) and Uniform Resource Locators (URLs). Uniform Resource Characteristics (URCs) are discussed in this document but only as descriptions of resources rather than identifiers. A service in the network providing access to a resource may provide one or some of these options, but it need not provide all of them. This memo specifies an initial set of these functions, to be used to describe the functions provided by any given access service and the requirements that must be met when those operations are encoded in a protocol.