Transclusion is the inclusion of the content of a document into another document by reference. In the Wikipedian context, it is the use of the template functionality of MediaWiki to include the same content in multiple documents without having to edit those documents separately. Template transclusion is the common way to use template messages, and is implemented by using a template tag, with this form:

{{template name}}

Occasionally one may want to use a template, but for one reason or another may not want to use transclusion. The automatic one-time copying of a template's code/text to the location of a template tag is called Template substitution or subclusion (substitution + transclusion). To subclude a template's code/text, the template tag is modified from the standard transclusion tag to a substitution tag, simply by adding subst:, creating a tag with the form: {{subst:Template name}}.

[edit] How transclusion works

To transclude any source page (within a single MediaWiki project, such as en:Wikipedia), include the following code in the target page:

{{SOMEPAGE}}

Whenever the target page A with this code is rendered, the engine will include in that place not the code itself, but the entire content of the source page B, SOMEPAGE.

For example, you might decide to place a welcome message on every newcomer's Talk Page. Transclusion creates a "live" link between the template-page and the target-page(s) upon which the message should appear. When the template is edited, all the target-pages are edited too.

For example, you might decide to create a (template) page with your mailing address and include that template on not only your page, but all your friends' pages, too. When you move your television and couch to another apartment, you will change your address template, and automatically, that new information will appear on all your friends' pages.

[edit] Etymology

Ted Nelson coined the term "transclusion," as well as "hypertext" and "hypermedia", in his 1982 book, Literary Machines.

[edit] Partial transclusion

By using "noinclude", "onlyinclude" and "includeonly" markup, it is possible to transclude part of a page rather than all of it. Such partial transclusions can also be achieved by transcluding from other pages such as subpages. It is often useful not to transclude some information, such as template documentation.

For an example of how this technique can be applied to simplify the creation of summary articles, see Pathology, which consists of a collection of transcluded lead paragraphs from several main articles.

[edit] Transclusion markup

• noinclude. The markup <noinclude>...</noinclude> means that the text between the tags will not be transcluded onto another page, but will only appear on the page itself. This is useful for documentation.
• includeonly. The markup <includeonly>...</includeonly> means that the text between the tags will only be used when the page is transcluded onto another page, and will not appear on the page itself. This can be useful, for example, for adding categories to pages transcluding a template, without adding the template itself to these categories.
• onlyinclude. The markup <onlyinclude>...</onlyinclude> indicates that only text surrounded by "onlyinclude" markup should be transcluded onto another page. This is the most subtle of the partial transclusion tags because it often overrules the others. If there is at least one pair of "onlyinclude" tags on a page, then whenever this page is transcluded, it is only the material within the "onlyinclude" tags which gets transcluded. There can be several such sections, and within each such section, some material might be further excluded by "noinclude" tags, and might also be surrounded by "includeonly" tags so that it does not appear on the original page itself. But material outside the "onlyinclude" tags will be ignored when the page is transcluded onto another page. This can be useful, for example, to repeat a small part of one page on a second one: just surround the small part by onlyinclude tags, and transclude it onto the second page.

[edit] Subpages

One can cut and paste the text to be transcluded into a subpage, then use the name of the subpage in the transclusion template. This approach can only be used with subpages from User, Talk or Wikipedia pages; currently, subpages cannot be created from main article pages.

Example: you want to discuss the deletion and redirecting of Pussycat to Cat. First, create the subpage Talk:Pussycat/Let's delete Pussycat!, write your comment into it, then transclude it in Talk:Pussycat and Talk:Cat using the template {{Talk:Pussycat/Let's delete Pussycat!}}. Comments posted in either talk pages will be shown in both.

[edit] Special pages

Some pages on Special:Specialpages can be transcluded, such as Special:Allpages, Special:Prefixindex, Special:Newfiles, Special:Newpages, Special:Recentchanges and Special:Recentchangeslinked.

Samples:

• {{Special:Allpages/General}} – a list of pages starting at "General"
• {{Special:Prefixindex/General}} – a list of pages with prefix "General"
• {{Special:Newfiles/4}} – a gallery of the four most recently uploaded files
• {{Special:Newpages/5}} – a list of the five most recently created pages
• {{Special:Recentchanges/5}} – the five most recent changes
• {{Special:Recentchangeslinked/General}} – recent changes to the pages linked from "General"

Except for Special:Recentchangeslinked, the slash and the word/number after the slash can be omitted, giving a list of pages without a specific starting point, or a list of the default length.

[edit] Pages related to MediaWiki transclusion

• Wikipedia:MediaWiki namespace
  • m:Help:MediaWiki namespace
• m:Help:Variable
• Wikipedia talk:Template namespace#transcluding prose

[edit] Templates

• Help:Template
• Wikipedia:Template namespace
• Wikipedia:Template limits

[edit] See also

• Request for template transclusion from Commons (interwiki templates, etc.)
• Wikipedia:Substitution (the opposite of transclusion)