Uniform Resource Name
The relationship of URN to URI and URL

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.

The Functional Requirements for Uniform Resource Names are described in RFC 1737. The URNs are part of a larger Internet information architecture which is composed of URNs, Uniform Resource Characteristics (URCs), and Uniform Resource Locators (URLs). Each plays a specific role:

  • URNs are used for identification,
  • URCs for including meta-information.
  • URLs for locating or finding resources.

RFC 2141 ("URN Syntax") 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.

It is worth noting that, as stated in RFC 3986 ("Uniform Resource Identifier Generic Syntax"),

The term "Uniform Resource Name" (URN) has been used historically to refer to both URIs under the "urn" scheme (RFC 2141), which are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable, and to any other URI with the properties of a name.

Contents

URN Syntax

RFC 2141 (dated May 1997 and still classified as requests discussion and suggestions for improvements) describe in BNF the syntax of URNs as:

<URN> ::= "urn:" <NID> ":" <NSS>
where <NID> is the Namespace Identifier, and <NSS> is the Namespace Specific String. Phrases enclosed in quotes are REQUIRED. The leading "urn:" sequence is case-insensitive. The Namespace ID determines the syntactic interpretation of the Namespace Specific String.

Comparison with URLs

A URN is similar to a person's name, while a URL is like a street address. The URN defines something's identity, while the URL provides a location. Essentially, "what" vs. "where".

URNs are often compared to the ISBN system for uniquely identifying books (and in fact, it is possible to encode an ISBN as a URN). Having a book's unique identifier lets you discuss the book, such as whether you've read it, enjoyed it, etc. To actually read the book, however, you need its location (e.g., "on the bedside table"). So URNs and URLs are often complementary; for example, you might discuss an RFC using both concepts: "you can find urn:ietf:rfc:3187 (URN) over at http://tools.ietf.org/html/rfc3187.html (URL)."

Examples

urn:isbn:0451450523
The URN for The Last Unicorn (1968 book), identified by its book number.
urn:isan:0000-0000-9E59-0000-O-0000-0000-2
The URN for Spider-Man (2002 film) identified by its audiovisual number.
urn:issn:0167-6423
The URN for the Science of Computer Programming (scientific journal), identified by its serial number.
urn:ietf:rfc:2648
The URN for the IETF's RFC 2648.
urn:mpeg:mpeg7:schema:2001
Default Namespace Rules for MPEG-7 video metadata.
urn:oid:2.16.840
The URN corresponding to the OID for the United States.
urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66
A URN using a version 1 UUID.

Non-standard usage

The following are examples for "non-standard" URNs, i.e. identifiers that don't use officially registered (per RFC 3406) namespaces, which, though, match the syntax defined in RFC 2141 (URN Syntax).

urn:www.agxml.org:schemas:all:2:0
A non-standard URN representing a namespace for Schema "Agricultural Markup Language 2.0 for Grain and Oilseed Business".
urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C
A non-standard URN representing a specific MP3 file of the I have a dream speech by Martin Luther King by its SHA-1 hash Base32 encoded.
urn:tree:tiger:BL5OM7M75DWHAXMFZFJ23MU3LVMRXKFO6HTGUTY
A non-standard URN representing the same MP3 file this time using its Tiger Tree hash. Both these schemes can be used to look up data about specific files, for example using Bitzi.
urn:sici:1046-8188(199501)13:1%3C69:FTTHBI%3E2.0.TX;2-4
A specific article in the journal "ACM Transactions on Information Systems", identified by its percent-encoded SICI code.[1]

Resolvers

A URN resolver is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of a URN name or a "resolution request", e.g., a request for translation of a URN name into a URL.

An example server-side URN resolver: see RFC 2169.

See also

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Uniform Resource Name — Uniform Resource Name,   URN …   Universal-Lexikon

  • Uniform Resource Name — Pour les articles homonymes, voir URN. Uniform Resource Name (URN), traduit littéralement de l anglais par « nom uniforme de ressource », est le nom d un standard informatique dans le domaine de l Internet qui concerne principalement le …   Wikipédia en Français

  • Uniform Resource Name — Ein Uniform Resource Name (URN, engl.: einheitlicher Name für Ressourcen) ist ein Uniform Resource Identifier (URI) mit dem Schema urn, der als dauerhafter, ortsunabhängiger Bezeichner für eine Ressource dient. Inhaltsverzeichnis 1 Aufbau 1.1… …   Deutsch Wikipedia

  • Uniform Resource Name — URN (англ. Uniform Resource Name)  единообразное название (имя) ресурса. На английский манер произносится как [эорн], по русски чаще говорят [у эр эн]. URN  это постоянная последовательность символов, идентифицирующая абстрактный или физический… …   Википедия

  • Uniform Resource Name — universalusis ištekliaus vardas statusas T sritis informatika apibrėžtis Nuolatinis ištekliaus vardas, nepriklausantis nuo ištekliaus buvimo vietos (adreso) kompiuterių tinkle. Juo identifikuojamas išteklius gali būti pasiekiamas ir tada, kai… …   Enciklopedinis kompiuterijos žodynas

  • Uniform Resource Name — URN es un acrónimo inglés de Uniform Resource Name, en español Nombre de recurso uniforme . Un URN funciona de manera similar a un URL (Localizadores Universales de Recursos). Éstos identifican recursos en la web, pero a diferencia de un URL, no… …   Wikipedia Español

  • Uniform Resource Name —    Abbreviated URN. A proposal from the IETF (Internet Engineering Task Force) for a naming scheme that will identify Internet resources by name, irrespective of where they are located.    See also Uniform Resource Locator …   Dictionary of networking

  • Uniform Resource Identifier — In computing, a Uniform Resource Identifier (URI) is a compact string of characters used to identify or name a resource on the Internet. The main purpose of this identification is to enable interaction with representations of the resource over a… …   Wikipedia

  • Uniform Resource Identifier — Pour les articles homonymes, voir Uri (homonymie). Un URI, de l anglais Uniform Resource Identifier, soit littéralement identifiant uniforme de ressource, est une courte chaîne de caractères identifiant une ressource sur un réseau (par exemple… …   Wikipédia en Français

  • Uniform Resource Identifier — Un Uniform Resource Identifier o URI (en español identificador uniforme de recurso ) es una cadena de caracteres corta que identifica inequívocamente un recurso (servicio, página, documento, dirección de correo electrónico, enciclopedia, etc.).… …   Wikipedia Español

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”