Uniform Resource Name

A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the urn scheme.

URIs, URNs, and URLs

URNs were originally conceived to be part of a three-part information architecture for the Internet, along with Uniform Resource Locators (URLs) and Uniform Resource Characteristics (URCs), a metadata framework. As described in the 1994 RFC 1737,[1], and later in the 1997 RFC 2141 [2], URNs were distinguished from URLs, which identify resources by specifying their locations in the context of a particular access protocol, such as HTTP or FTP. In contrast, URNs were conceived as persistent, location-independent identifiers assigned within defined namespaces, typically by an authority responsible for the namespace, so that they are globally unique and persistent over long periods of time, even after the resource which they identify ceases to exist or becomes unavailable.[3]

URCs never progressed past the conceptual stage,[4] and other technologies such as the Resource Description Framework later took their place. Since RFC 3986[5] in 2005, use of the terms "Uniform Resource Name" and "Uniform Resource Locator" has been deprecated in technical standards in favor of the term Uniform Resource Identifier (URI), which encompasses both, a view proposed in 2001 by a joint working group between the World Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF).[4]

A URI is a string of characters used to identify a name or resource. URIs are used in many Internet protocols to refer to and access information resources. URI schemes include the familiar http, as well as hundreds of others.

In the "contemporary view", as it is called, all URIs identify or name resources, perhaps uniquely and persistently, with some of them also being "locators" which are resolvable in conjunction with a specified protocol to a representation of the resources.

Other URIs are not locators and are not necessarily resolvable within the bounds of the systems where they are found. These URIs may serve as names or identifiers of resources. Since resources can move, opaque identifiers which are not locators and are not bound to particular locations are arguably more likely than identifiers which are locators to remain unique and persistent over time. But whether a URI is resolvable depends on many operational and practical details, irrespective of whether it is called a "name" or a "locator". In the contemporary view, there is no bright line between "names" and "locators".

In accord with this way of thinking, the distinction between Uniform Resource Names and Uniform Resource Locators is now no longer used in formal Internet Engineering Task Force technical standards, though the latter term, URL, is still in wide informal use.

The term "URN" continues now as one of more than a hundred URI "schemes", urn:, paralleling http:, ftp:, and so forth. URIs of the urn: scheme are not locators, are not required to be associated with a particular protocol or access method, and need not be resolvable. They should be assigned by a procedure which provides some assurance that they will remain unique and identify the same resource persistently over a prolonged period. Some namespaces under the urn: scheme, such as urn:uuid: assign identifiers in a manner which does not require a registration authority, but most of them do. A typical URN namespace is urn:isbn, for International Standard Book Numbers. This view is continued in the 2017 RFC 8141 [3].

There are other URI schemes, such as tag:, info: (now largely deprecated), and ni:[6] which are similar to the urn: scheme in not being locators and not being associated with particular resolution or access protocols.


The syntax of a urn: scheme URI is represented in the augmented Backus–Naur form as:[7]

      namestring    = assigned-name
                      [ rq-components ]
                      [ "#" f-component ]
      assigned-name = "urn" ":" NID ":" NSS
      NID           = (alphanum) 0*30(ldh) (alphanum)
      ldh           = alphanum / "-"
      NSS           = pchar *(pchar / "/")
      rq-components = [ "?+" r-component ]
                      [ "?=" q-component ]
      r-component   = pchar *( pchar / "/" / "?" )
      q-component   = pchar *( pchar / "/" / "?" )
      f-component   = fragment

or, in the form of a syntax diagram, as:

URN syntax diagram - namestring

URN syntax diagram - namestring
  • The leading scheme (urn:) is case-insensitive.
  • <NID> is the namespace identifier, and may include letters, digits, and -.
  • The NID is followed by the namespace-specific string <NSS>, the interpretation of which depends on the specified namespace. The NSS may contain ASCII letters and digits, and many punctuation and special characters. Disallowed ASCII and Unicode characters may be included if percent-encoded.

In 2017 the syntax for URNs was updated as follows:[3]

  • The slash character (/) is now allowed in the NSS to represent names containing slashes from non-URN identifier systems.
  • The q-component was added to enable passing of parameters to named resources.
  • The r-component was added to enable passing of parameters to resolvers. However, the updated specification notes that the r-component should not be used until its semantics are defined via further standardization.


In order to ensure the global uniqueness of URN namespaces, their identifiers (NIDs) are required to be registered with the IANA. Registered namespaces may be "formal" or "informal". An exception to the registration requirement was formerly made for "experimental namespaces"[8], since rescinded by RFC 8141.[3]


Approximately sixty formal URN namespace identifiers have been registered. These are namespaces where Internet users are expected to benefit from their publication,[3] and are subject to several restrictions. They must:

  • Not be an already-registered NID
  • Not start with urn-
  • Be more than two letters long
  • Not start with XY-, where XY is any combination of two ASCII letters
  • Not start with x- (see "Experimental namespaces", below)


Informal namespaces are registered with IANA and assigned a number sequence (chosen by IANA on a first-come-first-served basis) as an identifier,[3] in the format

"urn-" <number>

Informal namespaces are fully fledged URN namespaces and can be registered in global registration services.[3]


An exception to the registration requirement was formerly made for "experimental namespaces".[8] However, following the deprecation of the "X-" notation for new identifier names [9], RFC 8141 [3] did away with experimental URN namespaces, indicating a preference for use of the urn:example namespace where appropriate.[10]


URN corresponds to
urn:isbn:0451450523 The 1968 book The Last Unicorn, identified by its book number.
urn:isan:0000-0000-9E59-0000-O-0000-0000-2 The 2002 film Spider-Man, identified by its audiovisual number.
urn:ISSN:0167-6423 The scientific journal Science of Computer Programming, identified by its serial number.
urn:ietf:rfc:2648 The IETF's RFC 2648.
urn:mpeg:mpeg7:schema:2001 The default namespace rules for MPEG-7 video metadata.
urn:oid:2.16.840 The OID for the United States.
urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66 A version 1 UUID.
urn:nbn:de:bvb:19-146642 A National Bibliography Number for a document, indicating country (de), regional network (bvb = Bibliotheksverbund Bayern), library number (19) and document number.
urn:lex:eu:council:directive:2010-03-09;2010-19-UE A directive of the European Union, using the proposed Lex URN namespace.
urn:lsid:zoobank.org:pub:CDC8D258-8F57-41DC-B560-247E17D3DC8C A directive of the Life Science Identifiers may be resolved to http://zoobank.org/urn:lsid:zoobank.org:pub:CDC8D258-8F57-41DC-B560-247E17D3DC8C .

See also



  1. ^ RFC 1737 (1994).
  2. ^ RFC 2141 (1997).
  3. ^ a b c d e f g h RFC 8141 (2017).
  4. ^ a b W3C/IETF (2001).
  5. ^ RFC 3986 (2005).
  6. ^ "Naming Things with Hashes".
  7. ^ RFC 8141, section 2 (2017).
  8. ^ a b RFC 3406 (2002).
  9. ^ RFC 6648 (2012).
  10. ^ RFC 6963 (2013).


External links

Common Language Information Services

Common Language Information Services encompasses several products that are in general use by the global telecommunications industry through license agreements. Common Language products combine numerics and mnemonics to establish naming conventions that telecommunication companies use to exchange critical information via Operations Support Systems and other interface mechanisms.

Common Language codes help communications companies name, locate, inventory and manage all aspects of their networks. They identify items as large as a building, as small as a single board in a digital switching machine and as complex as a customer circuit. Telcordia manages the registry for all Common Language codes on behalf of the telecommunication service providers industry.

Common Language code sets are recognized by industry standards bodies and organizations, including ATIS, ANSI, IETF, and ETSI.

Computer network naming scheme

In computing, naming schemes are often used for objects connected into computer networks.

Digital object identifier

In computing, a Digital Object Identifier or DOI is a persistent identifier or handle used to uniquely identify objects, standardized by the International Organization for Standardization (ISO). An implementation of the Handle System, DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports and data sets, and official publications though they also have been used to identify other types of information resources, such as commercial videos.

A DOI aims to be "resolvable", usually to some form of access to the information object to which the DOI refers. This is achieved by binding the DOI to metadata about the object, such as a URL, indicating where the object can be found. Thus, by being actionable and interoperable, a DOI differs from identifiers such as ISBNs and ISRCs which aim only to uniquely identify their referents. The DOI system uses the indecs Content Model for representing metadata.

The DOI for a document remains fixed over the lifetime of the document, whereas its location and other metadata may change. Referring to an online document by its DOI is supposed to provide a more stable link than simply using its URL. But every time a URL changes, the publisher has to update the metadata for the DOI to link to the new URL. It is the publisher's responsibility to update the DOI database. If they fail to do so, the DOI resolves to a dead link leaving the DOI useless.

The developer and administrator of the DOI system is the International DOI Foundation (IDF), which introduced it in 2000. Organizations that meet the contractual obligations of the DOI system and are willing to pay to become a member of the system can assign DOIs. The DOI system is implemented through a federation of registration agencies coordinated by the IDF. By late April 2011 more than 50 million DOI names had been assigned by some 4,000 organizations, and by April 2013 this number had grown to 85 million DOI names assigned through 9,500 organizations.

Formal Public Identifier

A Formal Public Identifier (FPI) is a short piece of specially formatted text that may be used to uniquely identify a product, specification or document. One of their most common uses is as part of document type definitions, but they are also used in the vCard and iCalendar formats to identify the software product that has generated data.

More recently, Uniform Resource Identifiers (URIs) and universally unique identifiers (UUIDs) are usually used to uniquely identify objects. FPIs have become a legacy system.

ISO/IEC 6523

ISO/IEC 6523 Information technology – Structure for the identification of organizations and organization parts is an international standard that defines a structure for uniquely identifying organizations and parts thereof in computer data interchange and specifies the registration procedure to obtain an International Code Designator (ICD) value for an identification scheme.

The standard consists of two parts:

Part 1: Identification of organization identification schemes defines a structure for the identification of organizations and parts thereof. The components of this structure are the following:

an International Code Designator (ICD) value, which uniquely identifies the authority which issued the code to the organization, up to 4 digits

an organization identifier, up to a maximum of 35 characters

an (optional) organization part identifier (OPI), up to a maximum of 35 characters (An organization part can be any kind of entity within an organization.)

an (optional) OPI source indicator, 1 digit, specifying who attributed the OPIPart 2: Registration of organization identification schemes defines the registration procedure for ICD values. This includes:

the registration authority for ICD values is Farance Inc. on behalf of the American National Standards Institute (ANSI).

the specific procedures for the allocation and deletion of ICD values

the contents of the register/list of the registered identification schemes(A list of allocated ICD values is available here. An up-to-date list may also be acquired by contacting the registration authority.)

Further information concerning ISO/IEC 6523 and on how to obtain an ICD value can be found here.

ISO/IEC 6523 forms the basis of OSI naming under ISO/IEC 8348. It also forms the 1.3 object identifier (OID) tree.

The most widespread standard compliant with ISO 6523 norm is the identifier called "Global Location Number" (GLN), developed by GS1 company members. In B2B exchanges, it is widely used by companies to identify locations or functions within a location (for example : a factory, the accounting department of a company, an administration, a warehouse, a delivery address, ...). It has become a key to exchange business messages (orders, invoices, ...) using UN/EDIFACT specifications.

The ebCore Party Id Type Technical Specification was issued by the Organization for the Advancement of Structured Information Standards (OASIS). It was elaborated by the OASIS ebXML Core Technical Committee and it specifies a Uniform Resource Name (URN) namespace for organization identifiers. It bases upon ISO/IEC 6523, ISO 9735 and ISO 20022.

International Standard Serial Number

An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature.The ISSN system was first drafted as an International Organization for Standardization (ISO) international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard.

When a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in print and electronic media. The ISSN system refers to these types as print ISSN (p-ISSN) and electronic ISSN (e-ISSN), respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is also assigned a linking ISSN (ISSN-L), typically the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.


Life Science Identifiers are a way to name and locate pieces of information on the web. Essentially, an LSID is a unique identifier for some data, and the LSID protocol specifies a standard way to locate the data (as well as a standard way of describing that data). They are a little like DOIs used by many publishers.

An LSID is represented as a uniform resource name (URN) with the following format:

urn:lsid:::[:]The lsid: namespace, however, is not registered with the Internet Assigned Numbers Authority (IANA), and so these are not strictly URNs or URIs.LSIDs may be resolved in URLs, e.g. http://zoobank.org/urn:lsid:zoobank.org:pub:CDC8D258-8F57-41DC-B560-247E17D3DC8C

Lex (URN)

lex is a URN namespace, a type of Uniform Resource Name (URN), that allows accurate identification of laws and other legal norms.

LexML Brasil and Italy (Civil law countries) already do an official use of the URN LEX standard draft v0.9, as a namespace for sources of law.

Michael Mealling

Michael Mealling (born 1969) is co-founder of Pipefish Inc, and was the cofounder, Chief Financial Officer (CFO) and Vice President of Business Development of Masten Space Systems, CEO of Refactored Networks, long time participant within the IETF, a Space Frontier Foundation Advocate, and a former Director of the Moon Society. He operates a blog site called Rocketforge and has been interviewed twice on The Space Show and twice on SpaceVidcast.


In computing, a namespace is a set of symbols that are used to organize objects of various kinds, so that these objects may be referred to by name. In Java, a namespace ensures that all the identifiers within it must have unique names so that they can be easily identified. In order to manage the namespace Java provides the mechanism of creating Java packages. Prominent examples include:

file systems are namespaces that assign names to files;

some programming languages organize their variables and subroutines in namespaces;

computer networks and distributed systems assign names to resources, such as computers, printers, websites, (remote) files, etc.Namespaces are commonly structured as hierarchies to allow reuse of names in different contexts. As an analogy, consider a system of naming of people where each person has a proper name, as well as a family name shared with their relatives. If the first names of family members are unique only within each family, then each person can be uniquely identified by the combination of first name and family name; there is only one Jane Doe, though there may be many Janes. Within the namespace of the Doe family, just "Jane" suffices to unambiguously designate this person, while within the "global" namespace of all people, the full name must be used.

In a similar way, hierarchical file systems organize files in directories. Each directory is a separate namespace, so that the directories "letters" and "invoices" may both contain a file "to_jane".

In computer programming, namespaces are typically employed for the purpose of grouping symbols and identifiers around a particular functionality and to avoid name collisions between multiple identifiers that share the same name.

In networking, the Domain Name System organizes websites (and other resources) into hierarchical namespaces.

National Bibliography Number

National Bibliography Number (NBN) is a group of publication identifier systems used by national libraries in countries such as Germany, Italy, Finland, Norway, and Sweden. There is no global standard for the contents of NBNs; instead, they have a country-specific format. NBNs are typically used for documents which do not have a publisher-assigned identifier such as an ISBN. They can be used to identify persistently media that are archived in national libraries, for instance Ph.D. theses.

A Uniform Resource Name (URN) namespace for NBNs has been assigned [1], and is described in IETF RFC 3188. For example:

urn:nbn:de:bvb:19-146642An NBN in Germany (de), in Bavaria (bvb = Bibliotheksverbund Bayern), library number 19 (University Library Munich), pointing to a PhD thesis on heat detection in cattle.

Some libraries, such as the National Library of Sweden, provide a resolution service for these URNs.[2]

In Italy an NBN (NBN:IT) is assigned to digital resources deposited in the National Legal Deposit service [3]. The NBN:IT resolver is active at: http://nbn.depositolegale.it/

Object identifier

In computing, object identifiers or OIDs are an identifier mechanism standardized by the International Telecommunications Union (ITU) and ISO/IEC for naming any object, concept, or "thing" with a globally unambiguous persistent name.


Percent-encoding, also known as URL encoding, is a mechanism for encoding information in a Uniform Resource Identifier (URI) under certain circumstances. Although it is known as URL encoding it is, in fact, used more generally within the main Uniform Resource Identifier (URI) set, which includes both Uniform Resource Locator (URL) and Uniform Resource Name (URN). As such, it is also used in the preparation of data of the application/x-www-form-urlencoded media type, as is often used in the submission of HTML form data in HTTP requests.

Tag URI scheme

The tag URI scheme is a uniform resource identifier (URI) scheme for unique identifiers called tags, defined by RFC 4151 in October 2005.The RFC identifies four requirements for tags:

Identifiers are likely to be unique across space and time, and come from a practically inexhaustible supply.

Identifiers are relatively convenient for humans to mint (create), read, type, remember etc.

No central registration is necessary, at least for holders of domain names or email addresses; and there is negligible cost to mint each new identifier.

The identifiers are independent of any particular resolution scheme.Tags are used extensively in YAML.

Uniform Resource Characteristic

In computer science, a Uniform Resource Characteristic (URC) is a string of characters representing the metadata of a Uniform Resource Identifier (URI), a string identifying a Web resource. A URC binds a URI's associated Uniform Resource Name (URN), a unique name for a Web resource, to its Uniform Resource Locator (URL), the location at which a Web resource can be found. URCs were proposed as a specification in the mid-1990s, but were never adopted.

The use of a URC would allow the location of a Web resource to be obtained from its standard name, via the use of a resolving service. It was also to be possible to obtain a URC from a URN by the use of a resolving service. The design goals of URCs were that they should be simple to use, easy to extend, and compatible with a wide range of technological systems. The URC syntax was intended to be easily understood by both humans and software.

Uniform Resource Identifier

A Uniform Resource Identifier (URI) is a string of characters that unambiguously identifies a particular resource. To guarantee uniformity, all URIs follow a predefined set of syntax rules, but also maintain extensibility through a separately defined hierarchical naming scheme (e.g. "http://").

Such identification enables interaction with representations of the resource over a network, typically the World Wide Web, using specific protocols. Schemes specifying a concrete syntax and associated protocols define each URI. The most common form of URI is the Uniform Resource Locator (URL), frequently referred to informally as a web address. More rarely seen in usage is the Uniform Resource Name (URN), which was designed to complement URLs by providing a mechanism for the identification of resources in particular namespaces.

Urn (disambiguation)

An urn is a vase-like container.

Urn may refer to:

Urn (band), a gothic metal band

Urn problem of probability theory

Urn (Ne Obliviscaris album)The acronym URN may refer to:

Uniform Resource Name, an Internet identifier

Unique Reference Number, an identifier of UK schools

University Radio Nottingham, England


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