Uniform Resource Name (URN)
A Uniform Resource Name is a type of URI that uniquely identifies a resource by its name, and always uses the URN scheme.
Format
The format of the URN scheme is:
urn:<namespace identifier>:<namespace-specific string>
Namespace identifiers (NID) are case insensitive and follow a specific format of their own, which includes disallowed characters and sequences. The rules and standards have changed over time .
The namespace-specific string (NSS) is a resource identifier that is unique within a namespace. It is the combination of the NID and NSS that guarantees the URI is unique.
Note
A URN is not a locator and thus does not need to be resolvable. No protocol, access method, or location is required.
Examples
These examples show the URN scheme uniquely identifying resources. No direction is given on how to locate them.
| URN | Description |
|---|---|
| urn:ietf:rfc: 7230 | IETF specification 7230, HTTP/1.1 Message Syntax and Routing. |
| urn:uuid | A universally unique identified (UUID) |
| urn:isbn | An international standard book number (ISBN) |
Takeaway
A URN is a type of URI that uniquely identifies a resource by its name. No information about the resource location or how to access it is included. The URN was replaced by the standard URI using URN as the scheme.