Editing Uniform Resource Name (section)

==URIs, URNs, and URLs==
URNs were originally conceived to be part of a three-part [[information architecture]] for the Internet, along with [[Uniform Resource Locator|Uniform Resource Locators (URLs)]] and [[Uniform Resource Characteristic|Uniform Resource Characteristics (URCs)]], a [[metadata]] framework.  As described in {{IETF RFC|1737}},{{sfnp|RFC 1737|1994}} and later in {{IETF RFC|2141|link=no}},{{sfnp|RFC 2141|1997}} 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 identifier|persistent]], location-independent identifiers assigned within defined [[namespace]]s, 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.{{sfnp|RFC 8141|2017}}  

URCs never progressed past the conceptual stage,{{sfnp|W3C/IETF|2001}} and other technologies such as the [[Resource Description Framework]] later took their place.  Since {{IETF RFC|3986|link=no}}{{sfnp|RFC 3986|2005}} 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).{{sfnp|W3C/IETF|2001}}

A URI is a [[character string (computer science)|string]] of [[character (computing)|character]]s used to [[identifier|identify]] or [[name]]  a [[web resource|resource]] on the internet. URIs are used in many Internet protocols to refer to and access information resources. URI schemes include the <code>http</code> and <code>ftp</code> protocols, 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", <code>urn:</code>, paralleling <code>http:</code>, <code>ftp:</code>, and so forth.  URIs of the <code>urn:</code> 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 <code>urn:</code> scheme, such as <code>[[UUID|urn:uuid:]]</code> assign identifiers in a manner which does not require a registration authority, but most of them do. A typical URN namespace is <code>[[ISBN|urn:isbn]]</code>, for International Standard Book Numbers.  This view is continued in {{IETF RFC|8141|link=no}} (2017).{{sfnp|RFC 8141|2017}}

There are other URI schemes, such as <code>[[Tag URI scheme|tag:]]</code>, <code>[[Info URI scheme|info:]]</code> (now largely deprecated), and <code>ni:</code>{{sfnp|RFC 6920|2013}} which are similar to the <code>urn:</code> scheme in not being locators and not being associated with particular resolution or access protocols.