View source for Help:System message

{{h:h|editor toc}}{{MoveToMediaWikiRejected}}
The '''user language''' of a page rendering is:
*the language specified in the parameter ''[[mw:Manual:Parameters_to_index.php#Preference_overriding|uselang]]'' in the URL, e.g. http://meta.wikimedia.org/w/index.php?title=Help:System_message&uselang=de
*by default, for a logged-in user, the [[Help:Preferences#Interface_language|language selected in the  preferences]]
*by default, for a user who is not logged in, and for a logged-in user who has not specified a language in the preferences, the [[mw:Manual:$wgLanguageCode|site language]] given by {{xpdoc|gives=, here giving|CONTENTLANGUAGE}}; on Wikimedia wikis this is e.g. English (en) for Meta and Commons, German (de) for de.wikipedia.org, etc.

The user language determines the interface texts; also the page ''body'' may depend on the user language, because the result of parser function ''int'' does, and hence also the result of templates which call that function directly or indirectly (see [[:Category:User interface language dependent templates]]).

In principle for every language a set of ca. 1800 '''system messages''' in that language is provided in the '''message file''' languages/messages/Messages''languagecode''.php. With language code qqx the message keys are returned.

MediaWiki supports over 330 languages. For completeness of the language files see [[mw:Localisation statistics|localization statistics]].

As of October 2007 there were ca. 100 languages with a Wikipedia but without a language file. These Wikipedias usually had English as site language, and/or [[mw:Localisation#Old local translation system|translated the interface locally]]. However, nowadays creating the language file is a condition for opening a new language edition of Wikipedia, see {{ml|Meta:Language proposal policy|Requisites}}, and the translation is done on [[translatewiki.net]], so that number has decreased to a handful.

==MediaWiki namespace==
The '''MediaWiki namespace''' is one of the 16 standard MediaWiki [[Help:namespace|namespaces]]. It allows [[help:Administrators|administrators]] to change the default system messages. The MediaWiki namespace is enabled by <tt>{{h:mwg|UseDatabaseMessages}}=true;</tt>, which is the default.

For example, see [[MediaWiki:Aboutpage]], [[MediaWiki:Aboutpage/fr]], and [[MediaWiki:Aboutpage/de]].

However, MediaWiki:Sidebar''/language_code'' does not work (for a [[mw:MediaWiki:sidebar|sidebar]] for users with that interface language); instead, the page MediaWiki:Sidebar can refer to message IDs which provides link labels dependent on the user-specified interface language<!-- ! an example or link would be necessary here ! -->. If the message is neither defined in the message file concerned, nor on the MediaWiki page, the message in the message file for English is used.

When viewing a "non-existing" page of which the name is an existing message name, the page shows the default.  A "non-existing" page can be recognized by the lack of a history link. When editing such a page, the default is automatically preloaded into the edit window. Transclusion of a "non-existing" page in the MediaWiki namespace trancludes the default.

For the names of all "existing" pages see [{{fullurl:Special:Allpages|from=MediaWiki:%21}} @] [[Special:Prefixindex/MediaWiki:A|A]] [[Special:Prefixindex/MediaWiki:B|B]] [[Special:Prefixindex/MediaWiki:C|C]] [[Special:Prefixindex/MediaWiki:D|D]] [[Special:Prefixindex/MediaWiki:E|E]] [[Special:Prefixindex/MediaWiki:F|F]] [[Special:Prefixindex/MediaWiki:G|G]] [[Special:Prefixindex/MediaWiki:H|H]] [[Special:Prefixindex/MediaWiki:I|I]] [[Special:Prefixindex/MediaWiki:J|J]] [[Special:Prefixindex/MediaWiki:K|K]] [[Special:Prefixindex/MediaWiki:L|L]] [[Special:Prefixindex/MediaWiki:M|M]] [[Special:Prefixindex/MediaWiki:N|N]] [[Special:Prefixindex/MediaWiki:O|O]] [[Special:Prefixindex/MediaWiki:P|P]] [[Special:Prefixindex/MediaWiki:Q|Q]] [[Special:Prefixindex/MediaWiki:R|R]] [[Special:Prefixindex/MediaWiki:S|S]] [[Special:Prefixindex/MediaWiki:T|T]] [[Special:Prefixindex/MediaWiki:U|U]] [[Special:Prefixindex/MediaWiki:V|V]] [[Special:Prefixindex/MediaWiki:W|W]] [[Special:Prefixindex/MediaWiki:X|X]] [[Special:Prefixindex/MediaWiki:Y|Y]] [[Special:Prefixindex/MediaWiki:Z|Z]]

For all supported languages, all default messages and current versions can be viewed at '''[[Special:Allmessages]]'''. When creating a page to override the default it is useful to first save the default version, to allow diffs with it.

An administrator with access to the language files can choose between adapting these and creating pages in the MediaWiki namespace. The latter makes it easier to update to a new version of MediaWiki while keeping the own versions of messages. On the other hand, is easier to transfer a language file to another MediaWiki site than to export and import pages, for the benefit of users who have selected the language concerned as interface language.

Also, an administrator can add extra pages to the MediaWiki namespace, to be accessed, for example, by function ''int'' (e.g. [[MediaWiki:Lang]]), or by a [[Special:Gadgets|gadget]]. These are not shown in [[Special:Allmessages]].

An extension can set e.g. message key aaa to bbb by:

   global $wgMessageCache;
   $wgMessageCache->addMessages( array ('aaa' => 'bbb') );

The key has to start with a lowercase letter, even though message files define messages using an ID written with a capital, and even though the corresponding MediaWiki page has a capital after the colon, in this case MediaWiki:Aaa, even on wikis which allow a lowercase first letter in page names. (The default content of MediaWiki:aaa becomes bbb, but changing it has no effect.)

After getting the array $ma of extension messages:
   $ma = $wgMessageCache->getExtensionMessagesFor( 'en' );
the value can be retrieved with $ma['aaa'], e.g. by:
   $wgOut->addWikiText( $ma['aaa'] );

The result after possible overriding by the contents of the MediaWiki page can be retrieved by wfMsg('aaa').

This applies not only for a message in the strict sense; for example, an extension can allow the user community, through an administrator, to supply parameters in this way; this can even be the name of an extension tag, see e.g. [[mw:Extension:PropertyTable]], where the tag <nowiki><</nowiki>properties> is the default, but e.g. the tag <nowiki><</nowiki>pr> can be used after creating the page "MediaWiki:propertyTable tag" with the content "pr" (but note that for portability of wikitext across wikis with the same extension this flexibility has also disadvantages).

All characters of namespace prefixes are case-insensitive, so one can write "mediawiki:".

LocalSettings.php can set messages too, see [http://lists.wikimedia.org/pipermail/wikitech-l/2009-March/042148.html thread].

== MediaWiki before version 1.9.x ==

The concept of messages has changed in [http://svn.wikimedia.org/svnroot/mediawiki/tags/REL1_9_0/phase3/RELEASE-NOTES release 1.9.x] (January 10, 2007). Before, there existed a page for each message, even if it was the default. On upgrade, all pages with default messages are deleted.

==Protection==

By default, the whole MediaWiki namespace is protected. This is necessary for a number of reasons:

* Many messages are in plain HTML, hence users could insert malicious scripts
* Vandalism of some messages would be extremely disruptive, for example changes to the text of the links in the sidebar would immediately be visible to all users

On the other hand, especially for pages MediaWiki:''message_ID/language_code'' the protection is somewhat impractical because administrators do not know all the languages that can be set for the user interface. 

If an administrator wishes to allow general editing of a system message, a template call can be placed in the MediaWiki page, with the template containing the message itself.

A few messages can in theory cause the software to stop working if they are changed, for example "linktrail". Therefore and for processing efficiency the effect of page [[MediaWiki:Linktrail]] has been disabled: the software ignores its contents, taking the regular expression straight out of the message files.

==Technical details==

The namespace number of {{ns:8}} messages is '''8''', with a corresponding {{ns:9}} namespace '''9''' to discuss individual messages.
Some MediaWiki wikis offer templates like {{links-small|w|template|editprotected}} to propose modifications, others have a page like
[[m:Meta:Requests for help from a sysop or bureaucrat|Meta:Requests for help from a sysop or bureaucrat]] for this purpose.

For links to MediaWiki messages, existence detection applies to existence of the message, not existence of the page:
*{{xpdplain|[|[mediawiki:1movedto2]]}} - link to non-existing page (view mode) for existing message
*{{xpdplain|[|[mediawiki:1movedto3]]}} - link to non-existing page (edit mode) for non-existing message
*{{xpdplain|[|[w:de:MediaWiki:Edit]]}}
*{{xpdplain|[{{fullurl:m:MediaWiki:Edit|action=render}} demo]}}

Each message in the <code>$wgAllMessagesEn</code> array in [http://svn.wikimedia.org/svnroot/mediawiki/trunk/phase3/languages/Messages.php Messages.php] corresponds to a page in the MediaWiki namespace. For example, there is a line in the php file:

 'protect-text' =&gt; 'Protect-text',

To this corresponds the page [[MediaWiki:Protect-text]], and {{xpdoc|int:Protect-text}}. When this page is edited the new message is automatically used for say {{fullurl:m:Main page|action=protect}}. Similarly [[w:fr:MediaWiki:Protect-text]] has the content <em>Confirmer la protection</em>, note that the page name itself is not translated.

===Transclusion===
Transclusion of a system message can be done with the regular tranclusion syntax for the MediaWiki page, even if the page does not exist and the default is used:
:{{xpdoc|mediaWiki:edit}}, the content of [[MediaWiki:Edit]], or if it does not exist, the system message with id "edit" for the site language
Also, [[Help:parser function|parser function]] '''int''' can be used (for an application, see e.g. [[Template:Ed]]):
:{{xpdoc|int:edit}}, the content of MediaWiki:Edit/xx where xx is the user language, or if it does not exist, the system message with id "edit" for this language. 

If there is neither a page nor a default the result of "int" is different from "MediaWiki:" even if the user uses the default interface language of the site:
:{{xpdoc|mediaWiki:erehwon}}
:{{xpdoc|int:erehwon}}
Messages defined in extensions, even if they are in [[Special:Allmessages]],  may or may not be transcluded:
:{{xpdoc|mediaWiki:dynamicpagelist noresults}}
:{{xpdoc|mediaWiki:expandtemplates}}

However many messages are not suited for inclusion, because they contain '''$1''' and similar parameters not evaluated by the
template parser, or raw [[w:Cascading Style Sheets|CSS]] and [[w:en:XHTML|XHTML]] markup not permitted on normal pages.

While $1, $2, etc. do not work as parameters when using "mediawiki":
*{{xpdop3p3c|mediawiki:revertpage|||a|||b}}
they do when using "int":
*{{xpdop3p3c|int:revertpage|||a|||b}}

===Error messages===
Error messages are in the site language, e.g. {{xpdoc|#expr:a}}. This allows branching depending on the type of error, independent of the user language. Note however that wikitext for such branching has to be adapted when transferring it to a wiki with an other site language. This is not needed in the case of  branching depending on whether any error occurs, with <code>#iferror</code>.

===Interlanguage links===
[[Help:Interwiki linking|Interlanguage link]]s in MediaWiki messages typically do not work: noinclude tags and the link syntax may not be interpreted.

Instead, one can use in-page interlanguage links on the talk pages, [[Template:Ilm]] does this for some major MediaWiki wikis.

===Strings exclusive to language file===
Some text strings cannot be customised using this feature, and so can only be changed by editing the language file:

* The namespace titles "User", "Wikipedia", "Image", etc. ($namespaceNames)
* The names of the special pages ($specialPageAliases)
*$skinNames (shown in [[Special:Preferences]])
*$bookstoreList
*$separatorTransformTable
*$linkTrail
*$dateFormats

== Branching based on the user language==
We have seen that the result of expansion of wikitext can depend on the user language through the use of "int". The exact behaviour with that regard is not completely clear and may change in the future (see in particular bugs [[bugzilla:1495|1495]] and its duplicate [[bugzilla:8188|8188]] for Commons, [[bugzilla:13010|13010]] and [[bugzilla:2085|2085]]; [[mw:Manual:$wgForceUIMsgAsContentMsg|$wgForceUIMsgAsContentMsg]]).

In addition to the possibility of directly storing the alternative texts in the MediaWiki namespace we can also use "int" only to find the code of the user language, and then use any branching method.  

The code of the user language is not directly available, but can be obtained with <code><nowiki>{{int:lang}}</nowiki></code> after creating a collection of pages Mediawiki:lang/xx, each containing the corresponding language code xx, see e.g. [http://commons.wikimedia.org/w/index.php?title=Special%3APrefixIndex&prefix=lang&namespace=8]:
:{{xpdoc|int:lang}} (gives the code of the user language if the MediaWiki page has been created, otherwise <lang>)
and using [[Template:Uselang]]:
:{{xpdoc|uselang}} (gives the code of the user language if the MediaWiki page has been created, otherwise en)

Thus, while internationalization of month names can be done directly:
:{{xpdoc|int:January}}
we can now adapt the format to the language, e.g.

:<code><nowiki>17{{#switch:{{int:lang}}|de=.}} {{int:January}} 2010</nowiki></code> gives 17{{#switch:{{int:lang}}|de=.}} {{int:January}} 2010.

or more generally, apply [[Template:Date]], where the default language is the user language, determined inside the template.

If a separate page is used for every language version, this is commonly done with the naming scheme pagename/xx for the language with code xx (just like in the MediaWiki namespace). The templates in [[:Category:Autotranslated templates]] use [[Template:Autotranslate]], which is based on this naming scheme, and selects the local version of a template. It checks existence and applies a fall-back scheme (see also [[commons:Template:Fallback]]). If the tasks of the language versions have much in common, such as computations, or formatting unrelated to language, then it is practical to let them call a common auxiliary template, with as parameters language specific data, such as texts, see e.g. [[Template:Unblock granted/layout]], [[commons:Template:Creator/layout]], [[commons:Template:Museum/layout]], and [[commons:Template:TemplateBox/layout]].

==See also==
*[[w:Wikipedia:Editnotice]]
*[[mw:Localisation]]
*[[mw:Localisation statistics]]
*[[mw:Manual:Special pages#MessageCache.php|The message cache]] - possibly not up-to date
*[[Help:MediaWiki namespace/old|MediaWiki namespace in version 1.2.6]]
*[[w:Wikipedia:MediaWiki namespace]]
*[[Help:User style]] - site-wide CSS and JS is partly defined in "system message" "common.css", etc.
*[[mw:Extension:Multilang]] - extension to create content depending on the user-specified interface language
*[[Special:Allmessages]] in various languages: {{messages|de}} {{messages|eo}} {{messages|en}} {{messages|fr}} {{messages|he}} {{messages|id}} {{messages|ja}} {{messages|la}} {{messages|nl}} {{messages|zh-yue|yue}}
*[[List of Wikipedias/sortable]] (column Lif) - links to [[Help:Interface demo]] with uselang=xx, for showing the interface on Meta with a specified interface language. 
*[http://svn.wikimedia.org/viewvc/mediawiki/trunk/phase3/languages/messages/ message files]
*[[Meta:Language select]] - internationalization system where all translations are sent to the browser; through css in combination with JavaScript the text in the browser language is displayed, with a selection box to choose another language; if the browser language or selected language is not supported, or by pressing a button, all translations are shown

{{h:f|enname=System message}}

[[Category:Multilingualism]]
[[Category:Editor handbook]]