Identifies a persistent Internet resource. A URN can provide a mechanism for locating and retrieving a schema file that defines a particular namespace. While an ordinary URL could provide similar functionality, a URN is more robust and easier to manage for this purpose because a URN can refer to more than one URL. URNs are not location-dependent as URLs are.
A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the urn scheme, and does not imply availability of the identified resource. Both URNs (names) and URLs (locators) are URIs, and a particular URI may be a name and a locator at the same time.