Transclusion (or transclude in its verb form )is a general idea in composing documents. Along with Hyperlink, the two of them provides a set of complementary functions to enable document compositionality. For MediaWiki users who wants to use transclusion effectively, the MediaWiki Transclusion page is a must read. This idea originally came from Ted Nelson's book on Literary Machine.

MediaWiki and Transclusion

It enables a crucial asIt is a particularly important feature in MediaWiki, which is often encoded using the {{:<Transclusion Page Name>}}. (Note the : colon sign in front of the page name.) In PKC, it is intentionally related to the notion of Pullback in Category Theory.