Uniform Resource Name definition
A Uniform Resource Name is a permanent identifier within the broader Uniform Resource Identifier (URI) system. As the name suggests, Uniform Resource Names identify the resource itself rather than its location.
Uniform Resource Names are one of the three primary types of URIs, the other two being Uniform Resource Locators (URLs) and the seldom-seen Uniform Resource Characteristics (URCs).
How Uniform Resource Names work
A Uniform Resource Name provides a unique and persistent identifier for a resource without necessarily indicating where it can be found. These identifiers are expected to be globally unique and persistent over time — once assigned, the Uniform Resource Name should remain unchanged, even if the resource is moved.
Uniform Resource Names typically start with the “urn:” prefix, followed by a NID (namespace identifier) for the responsible naming authority and the resource’s NSS (namespace-specific string). For example, “urn:isbn:0451450523” refers to the 1968 book The Last Unicorn, where “isbn” (International Standard Book Number) is the NID and “0451450523” is the NSS.
To avoid conflicts, Uniform Resource Name namespaces are frequently organized into hierarchies. In the above example using the ISBN, you could introduce sub-namespaces for different publishers to make sure that the identifiers are unique within their respective namespaces.