URN (Uniform Resource Name) is another type of URI (Uniform Resource Identifier), used to provide a persistent and location-independent identifier for a resource. Unlike URLs, which identify the location of a resource, URNs are intended to provide a stable and long-lasting identifier for a resource, regardless of its location.
A URN typically consists of a hierarchical sequence of namespaces and an identifier, separated by colons. The namespaces provide a context for the identifier and help to ensure its uniqueness. For example, the URN “urn:isbn:0-486-27557-4” identifies a book by its International Standard Book Number (ISBN), which is a unique identifier assigned to each published book.
The primary advantage of using URNs is that they provide a stable and persistent identifier for a resource, even if the resource is moved to a different location or if the location changes. This can be particularly useful for resources that are likely to be moved or renamed, or for resources that do not have a fixed location, such as digital objects in a distributed system.
URNs are used less frequently than URLs, but they are still an important part of the web infrastructure, particularly in the context of digital libraries, archives, and other types of digital repositories.