Uniform Resource Name

A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the "urn" scheme, and does not connote availability of the identified resource.

RFC 2141 says:

Uniform Resource Names (URNs) are intended to serve as persistent, location-independent resource identifiers and are designed to make it easy to map other namespaces (that share the properties of URNs) into URN-space. Therefore, the URN syntax provides a means to encode character data in a form that can be sent in existing protocols, transcribed on most keyboards, etc.

Suppose you own a copy of the book The Last Unicorn.

If you tell someone, "My copy of the book is on the lightstand in my bedroom," that's like a URL — you're telling someone where something is.

But if you tell someone, "I read a neat book; it's called The Last Unicorn," then that's like a URN — you're telling someone the name of something.

A person who knows where a particular copy is can get it for you, or tell someone else where it is. (URL)

A person who knows its name can reason about it, they can tell if they've seen it before, and maybe they can talk about what's inside the story. (URN)

Some URN values:

• "urn:isbn:0451450523" - the URN for "The Last Unicorn", identified by its book number.
• "urn:ietf:rfc:3187" - the URN for the IETF's RFC 3187.
• "urn:oid:2.16.840" - the URN corresponding to the OID for the United States.
• "urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C" - the URN representing the exact MP3 file of a speech by Martin Luther King.
• "urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66" - a URN using a version 1 UUID.

You could tell somebody: "You can find urn:ietf:rfc:3187 (URN) over at http://www.faqs.org/rfcs/rfc3187.html (URL)."

Both URNs and URLs are URIs.

See also

DOI (digital object identifier), PURL

External links

• Uniform Resource Names Charter - The IETF's Uniform Resource Names working group
• IANA URN namespace assignments