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Uniform Resource Name

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!!! Overview
[{$pagename}] ([URN]) is the historical name for a [Uniform Resource Identifier] ([URI]) that uses the urn scheme.
Defined in [1997|Year 1997] in [RFC 2141], [{$pagename}]s were intended to serve as __persistent__, __location-independent__ identifiers, allowing the simple mapping of [namespaces] into a single [URN] [namespace].
The existence of such a [URI] does not imply availability of the identified resource, but such [URIs] are required to remain globally __unique__ and __persistent__, even when the resource ceases to exist or becomes unavailable. [RFC 3986]
Since [RFC 3986] in [2005|Year 2005], the use of the term has been deprecated in favor of the less-restrictive "[URI]", a view proposed by a joint working group between the [World Wide Web Consortium] ([W3C]) and [Internet Engineering Task Force] ([IETF]).
Both [URNs] and [Uniform Resource Locators] ([URLs]) are [URIs], and a particular [URI] may be a name as well as a locator at the same time.
[URNs] were originally intended in the 1990s to be part of a three-part information architecture for the Internet, along with [URLs] and [Uniform Resource Characteristics] ([URC]s), a metadata framework. However, [URC]s never progressed past the conceptual stage, and other technologies such as the [Resource Description Framework] later took their place.
!! Syntax
The syntax of a [URN] is represented in [BNF] form as:
%%prettify
{{{
<URN> ::= "urn:" <NID> ":" <NSS>
}}} /%
This renders as:
* urn:<NID>:<NSS> - The leading urn: sequence is case-insensitive. <NID> is the [Namespace Identifier], which determines the syntactic interpretation of <NSS>, the namespace-specific string. The functional requirements for Uniform Resource Names are described in [RFC 1737].
* Namespaces - In order to ensure the global uniqueness of URN namespaces, their identifiers ([NIDs]) are required to be [registered|IANA Registry] with the [IANA]. Registered namespaces may be "formal" or "informal". An exception to the registration requirement is made for "experimental namespaces"
! Formal
Formal namespaces are those where some Internet users are expected to benefit from their publication,([RFC 3406]) and are subject to several restrictions. They must:
* not be an already-registered [NID]
* not start with x- (see "Experimental namespaces", below)
* not start with urn-
* not start with XY-, where XY is any combination of two ASCII letters
* be more than two letters long.
! Informal
Informal namespaces are registered with [IANA] and assigned a number sequence (chosen by [IANA] on a first-come-first-served basis) as an identifier, in the format
%%prettify
{{{
"urn-" <number>
}}} /%
Informal namespaces are fully fledged URN namespaces and can be registered in global registration services.
!! Experimental
Experimental namespaces take the form
%%prettify
{{{
"X-" <NID>
}}} /%
Namespaces of this form are intended only for use within internal or limited experimental contexts, and are not required or expected to be globally unique.
[RFC 6648] [deprecated] the use of "X-" notation for new ID names, but makes no recommendation on substituting existing "X-" names, and does not override existing specifications that require the use of "X-".
!! [URIs, URLs, and URNs]
What is the difference between [URIs, URLs, and URNs]?
!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
----
* [#1] - [Uniform_Resource_Name|Wikipedia:Uniform_Resource_Name|target='_blank'] - based on data observed:2016-08-03
This page (revision-1) was last changed on 29-Nov-2024 16:16 by UnknownAuthorTop