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Reverse domain name notation (or reverse-DNS) is a naming convention for components, packages, types or file names used by a programming language, system or framework. Reverse-DNS strings are based on registered domain names, with the order of the components reversed for grouping purposes. For example, if a company making the product "MyProduct" has the domain name example.com, they could use the reverse-DNS string com.example.MyProduct as an identifier for that product. Reverse-DNS names are a simple way of eliminating namespace collisions, since any registered domain name is globally unique to its owner (with alt roots making exceptions to this rule possible but unlikely).

History

The first appearance of reversed DNS strings predated the Internet domain name standards. The UK Joint Academic Networking Team (JANET) used this order in its Name Registration Scheme, before the Internet domain name standard was established. For example, the name uk.ac.bris.pys.as was interpreted as a host named as within the UK (top level domain .uk), while the Internet standard would have interpreted it as a host named uk within the American Samoa top level domain (.as). During the period while both JANET-style and Internet-style addresses were in use, mailers and gateway sites had ad-hoc workarounds to handle the differences, but could still be confused.

Reverse-DNS for identifier strings first became widely used with the Java platform.^{[citation needed]}

Examples

Examples of systems that use reverse-DNS notation are:

Java generally uses it for namespaces, including packages and modules
Apple's Uniform Type Identifier (UTI)^[1]
The Android operating system, for classifying applications (because the Dalvik virtual machine was based on Java)
dconf, the configuration backend used by GNOME
ginitd 'service' identifiers
The freedesktop.org Desktop Entry Specification^[2] and D-Bus Specification^[3]
Flatpak also uses a unique reverse-DNS identifier for each application, aligning with freedesktop.org standard^[4]
iSCSI Qualified Naming

Some examples of reverse-DNS strings are:

com.adobe.postscript-font, UTI string for Adobe Systems's PostScript fonts
com.apple.ostype, UTI string for Apple's OSType
org.omg.CORBA, Java library for CORBA
org.w3c.dom, Java library for W3C's DOM
com.eu.gershwin.DeviceManager, a ginitd service identifier commonly assigned to udev.
org.kde.dolphin.desktop, a desktop file name

References

^ "Apple Developer Connection: Introduction to Uniform Type Identifiers Overview". 2005-11-09. Retrieved 2013-04-04.
^ "Desktop Entry Specification". freedesktop.org. Retrieved 15 November 2020.
^ "D-Bus Specification". dbus.freedesktop.org.
^ "Requirements & Conventions". Flatpak.

External links

[1] "Apple Developer Connection: Introduction to Uniform Type Identifiers Overview". 2005-11-09. Retrieved 2013-04-04.

[2] "Desktop Entry Specification". freedesktop.org. Retrieved 15 November 2020.

[dbus-3] "D-Bus Specification". dbus.freedesktop.org.

[flatpak-4] "Requirements & Conventions". Flatpak.

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[2]

[3]

[4]

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+{{verify|date=May 2024}}
-The '''reverse domain name system''' (reverse-DNS), sometimes confused with [[Reverse DNS lookup]] or [[Reverse domain hijacking]], is system for naming components, packages, or types in computer systems. A characteristic of '''reverse-DNS''' strings is that they are based on registed [[Domain name|domain names]], only are reversed for sorting purposes. For example, if a company making a product called "MyProduct" has the registered [[Domain name|domain name]] "www.example.com", they could use the '''reverse-DNS''' string "com.example.MyProduct" to describe it.
+{{Short description|A reversed DNS name notation}}
+{{confuse|Reverse DNS lookup}}
+[[File:Android_9.0_Reverse-DNS_filesystem_hierarchy.png|thumb|An example of reverse-DNS filesystem hierarchy]]
+{{Wikifunctions|Z19112}}
+'''Reverse domain name notation''' (or '''reverse-DNS''') is a naming convention for components, packages, types or file names used by a programming language, system or framework. Reverse-DNS strings are based on registered domain names, with the order of the components reversed for grouping purposes. For example, if a company making the product "MyProduct" has the [[domain name]] <code>example.com</code>, they could use the reverse-DNS string <code>com.example.MyProduct</code> as an identifier for that product. Reverse-DNS names are a simple way of eliminating [[Naming_collision|namespace collisions]], since any registered domain name is globally unique to its owner (with [[alt root]]s making exceptions to this rule possible but unlikely).
 ==History==
+The first appearance of reversed DNS strings predated the Internet domain name standards.  The UK Joint Academic Networking Team ([[JANET]]) used this order in its [[JANET NRS|Name Registration Scheme]], before the Internet domain name standard was established. For example, the name <code>uk.ac.bris.pys.as</code> was interpreted as a host named <code>as</code> within the UK (top level domain <code>[[.uk]]</code>), while the Internet standard would have interpreted it as a host named <code>uk</code> within the American Samoa top level domain (<code>[[.as]]</code>). During the period while both [[big-endian|JANET-style]] and [[little-endian|Internet-style]] addresses were in use, mailers and gateway sites had ad-hoc workarounds to handle the differences, but could still be confused.
-'''Reverse-DNS''' first became widely used with the [[Java platform]], and has since been used for many other systems.{{Fact|date=July 2007}}
+Reverse-DNS for identifier strings first became widely used with the [[Java platform]].{{Citation needed|reason=need a source for the chronology and why they're particularly historic|date=January 2013}}
 ==Examples==
-Examples of systems that use '''reverse-DNS''' are [[Sun Microsystems]]' [[Java platform]] and [[Apple Inc.|Apple]]'s [[Uniform Type Identifier]].
+Examples of systems that use reverse-DNS notation are:
+* [[Java (software platform)|Java]] generally uses it for namespaces, including [[Java package|package]]s and [[Java Platform Module System|module]]s
+* [[Apple Inc.|Apple]]'s [[Uniform Type Identifier]] (UTI)<ref>{{cite web |url=https://developer.apple.com/library/mac/#documentation/FileManagement/Conceptual/understanding_utis/understand_utis_intro/understand_utis_intro.html |title=Apple Developer Connection: Introduction to Uniform Type Identifiers Overview|date=2005-11-09 |accessdate=2013-04-04}}</ref>
+* The [[Android (operating system)|Android]] operating system, for classifying applications (because the [[Dalvik (software)|Dalvik]] virtual machine was based on Java)
+* [[dconf]], the configuration [[Front and back ends|backend]] used by [[GNOME]]
+* ginitd 'service' identifiers
+* The [[freedesktop.org]] Desktop Entry Specification<ref>{{cite web |title=Desktop Entry Specification |url=https://specifications.freedesktop.org/desktop-entry-spec/ |publisher=freedesktop.org |accessdate=15 November 2020}}</ref> and D-Bus Specification<ref name="dbus">{{cite web |title=D-Bus Specification |url=https://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names |website=dbus.freedesktop.org}}</ref>
+* [[Flatpak]] also uses a unique reverse-DNS identifier for each application, aligning with freedesktop.org standard<ref name="flatpak">{{cite web |title=Requirements & Conventions |url=https://docs.flatpak.org/en/latest/conventions.html |website=Flatpak |language=en}}</ref>
+* [[ISCSI#Addressing|iSCSI Qualified Naming]]
+Some examples of reverse-DNS strings are:
+* <code>com.adobe.postscript-font</code>, [[Uniform Type Identifier|UTI]] string for [[Adobe Systems]]'s [[PostScript]] fonts
+* <code>com.apple.ostype</code>, [[Uniform Type Identifier|UTI]] string for [[Apple Inc.|Apple]]'s [[OSType]]
+* <code>org.omg.CORBA</code>, [[Java (programming language)|Java]] library for [[Common Object Request Broker Architecture|CORBA]]
+* <code>org.w3c.dom</code>, [[Java (programming language)|Java]] library for [[World Wide Web Consortium|W3C]]'s [[Document Object Model|DOM]]
+* <code>com.eu.gershwin.DeviceManager</code>, a ginitd service identifier commonly assigned to [[udev]].
+* <code>org.kde.dolphin.desktop</code>, a [[.desktop|desktop]] file name
+== See also ==
-Example of '''reverse-DNS''' strings are:
+* [[Non-Internet email address]]
-* com.adobe.postscript-font ([[Uniform Type Identifier|UTI]] string for [[Adobe]]'s [[PostScript]] fonts)
-* com.apple.ostype ([[Uniform Type Identifier|UTI]] string for [[Apple Inc.|Apple]]'s [[OSType]])
-* org.omg.CORBA ([[Java (programming language)|Java]] library for [[Common Object Request Broker Architecture|CORBA]])
-* org.w3c.dom ([[Java (programming language)|Java]] library for [[World Wide Web Consortium|W3C]]'s [[Document Object Model|DOM]])
+==References==
+{{Reflist}}
-== References ==
+==External links==
+* [https://github.com/eclipse-platform/eclipse.platform/blob/master/docs/Naming_Conventions.md Eclipse Naming Conventions]
-{{cite web|url=http://developer.apple.com/documentation/Carbon/Conceptual/understanding_utis/understand_utis_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001319-CH201-DontLinkElementID_15|title=Introduction to Uniform Type Identifiers Overview|date=[[2005-11-09]]|accessdate=2007-07-13}}
+* [https://gcc.gnu.org/ml/java/2000-04/msg00095.html Re: gnu.* namespace discussion]
+[[Category:Domain Name System]]
-== External Links ==
-* [http://wiki.eclipse.org/index.php/Naming_Conventions Eclipse Naming Conventions]
-* [http://gcc.gnu.org/ml/java/2000-04/msg00095.html Re: gnu.* namespace discussion]