Editing Namespace (section)

==Naming system==
A name in a namespace consists of a namespace name and a local name.<ref>{{cite web | url=http://www.w3.org/TR/REC-xml-names/ | title= Namespaces in XML 1.0 (Third Edition) | author=XML Core Working Group | work=W3C |date=8 December 2009 |access-date=2012-03-30}}</ref><ref>{{cite IETF  |title=URN Syntax |rfc=2141 |sectionname=Syntax |section=2 |page=1 |last= Moats |first= Ryan |date=May 1997 |publisher=[[Internet Engineering Task Force|IETF]] |access-date= 2012-03-30}}</ref> The namespace name is usually applied as a [[Prefix (computer science)|prefix]] to the local name.

In [[augmented Backus–Naur form]]:
<syntaxhighlight lang=abnf>
name = <namespace name> separator <local name>
</syntaxhighlight>
When local names are used by themselves, [[Name resolution (programming languages)|name resolution]] is used to decide which (if any) particular name is alluded to by some particular local name.

===Examples===
{| class=wikitable
|+ Examples of names in a namespace
|-
! Context !! Name !! Namespace name !! Local name
|-
| [[Path (computing)|Path]] || /home/user/readme.txt || /home/user (directory)|| readme.txt (file name)
|-
| [[Domain name]] || www.example.com || example.com (domain name)|| www (leaf domain name)
|-
| [[#Use in common languages|C++]] || std::array || std (C++ namespace)|| array (struct)
|-
| [[UN/LOCODE]] || US NYC  || US (country or territory)|| NYC (locality)
|-
| [[XML namespace|XML]] || xmlns:xhtml="http://www.w3.org/1999/xhtml" <br /> &lt;xhtml:body&gt; || xhtml (previously declared XML namespace xhtml="http://www.w3.org/1999/xhtml")|| body (element)
|- 
| [[Perl module#Perl packages and namespaces|Perl]] || $DBI::errstr || $DBI (Perl module)|| errstr (variable)
|-
| [[Java package|Java]] || java.util.Date || java.util (Java namespace)|| Date (class)
|-
| [[Uniform Resource Name]] (URN) || urn:nbn:fi-fe19991055 || urn:nbn (National Bibliography Numbers) || fi-fe19991055
|-
| [[Handle System]] || 10.1000/182  || 10 (handle naming authority) || 1000/182 (handle local name)
|-
| [[Digital object identifier]] || 10.1000/182 || 10.1000 (publisher) || 182 (publication)
|-
| [[MAC address]] || 01-23-45-67-89-ab  || 01-23-45 ([[organizationally unique identifier]]) || 67-89-ab (NIC specific)
|-
| [[PCI ID]] || 1234 abcd || 1234 (vendor ID) || abcd (device ID)
|-
| [[USB Implementers Forum#Obtaining a vendor ID|USB VID/PID]] || 2341 003f<ref>
Stephen J. Gowdy.
[http://www.linux-usb.org/usb.ids "List of USB ID's"].
2013.
</ref> || 2341 (vendor ID) || 003f (product ID)
|-
| [[SPARQL]] || dbr:Sydney || dbr (previously declared ontology, e.g. by specifying @prefix dbr: <http://dbpedia.org/resource/>) || Sydney 
|}
===Delegation===
Delegation of responsibilities between parties is important in real-world applications, such as the structure of the World Wide Web. Namespaces allow delegation of identifier assignment to multiple name issuing organisations whilst retaining global uniqueness.<ref>{{cite IETF  |title= Functional Requirements for Uniform Resource Names |rfc=1731 |sectionname=Requirements for functional capabilities |section=2 |page=3 |last= Sollins & Masinter |date=December 1994 |publisher=[[Internet Engineering Task Force|IETF]] |access-date= 2012-03-30}}</ref> A central [[Registration authority]] registers the [[National Internet registry|assigned namespace names allocated]]. Each namespace name is allocated to an organisation which is subsequently responsible for the assignment of names in their allocated namespace. This organisation may be a name issuing organisation that [[Metadata registry|assign the names]] themselves, or another [[Registration authority]] which further delegates parts of their namespace to different organisations.

===Hierarchy{{anchor|hierarchical namespace}}===
A naming scheme that allows subdelegation of namespaces to third parties is a '''hierarchical namespace'''.

A hierarchy is recursive if the syntax for the namespace names is the same for each subdelegation. An example of a recursive hierarchy is the [[Domain name|Domain name system]].

An example of a non-recursive hierarchy are [[Uniform Resource Name]] representing an [[Internet Assigned Numbers Authority]] (IANA) number.

{| class=wikitable
|+ Hierarchical namespace breakdown for urn:isbn:978-3-16-148410-0, an identifier for the book The Logic of Scientific Discovery by Karl Popper, 10th edition.
|-
! Registry !! Registrar !! Example Identifier !! Namespace name !! Namespace
|-
| [[Uniform Resource Name]] (URN) || [[Internet Assigned Numbers Authority]] || urn:isbn:978-3-16-148410-0 || urn || [https://www.iana.org/assignments/urn-namespaces/urn-namespaces.xml Formal URN namespace]
|-
| [[Uniform resource name|Formal URN namespace]] || [[Internet Assigned Numbers Authority]] || urn:isbn:978-3-16-148410-0 || ISBN || [http://tools.ietf.org/html/rfc3187 International Standard Book Numbers as Uniform Resource Names]
|-
| [[International Article Number (EAN)]] || [[GS1]] || 978-3-16-148410-0 || 978 || [[List of GS1 country codes|Bookland]]
|-
| [[International Standard Book Number]] (ISBN) || [[International ISBN Agency]] || 3-16-148410-X || 3 || [[German-speaking countries]]
|-
| [[International Standard Book Number#Publisher code|German publisher code]] || [http://www.german-isbn.de/ Agentur für Buchmarktstandards] || {{ISBNT|3-16-148410-X}} || 16 || [[Mohr Siebeck]]
|}

===Namespace versus scope===
A namespace name may provide context ([[Scope (computer science)|scope]] in computer science) to a name, and the terms are sometimes used interchangeably. However, the context of a name may also be provided by other factors, such as the location where it occurs or the syntax of the name.

{| class=wikitable
|+Examples of naming systems with local and global scope, and with and without namespaces
!   !! Without a namespace !! With a namespace
|-
| ''Local scope'' || [[Vehicle registration plate]] || [[Filesystem Hierarchy Standard]]
|-
| ''Global scope'' || [[Universally unique identifier]] || [[Domain Name System]]
|}