Transcluding

Transcluding is the inclusion of content from one document within another by reference, rather than duplicating the material. The included content is stored at a source location and retrieved when the host document is rendered, so the host appears to contain the material as if it were copied. The term was popularized by the Xanadu project led by Ted Nelson, which proposed that documents could reference shared passages rather than duplicate them.

Transclusion differs from embedding or simple copying in that the content shown is a live reference to the source. Updates to the original content can automatically appear in all documents that transclude it, and parameters may be supplied to customize how the content appears. Some systems perform transclusion at render time, while others fetch and cache content.

Common uses include wiki templates, where a single template page can be transcluded into many pages; content management systems that include reusable blocks; and document authoring with templating languages. In the wiki context, transclusion allows centralized maintenance of boilerplate text, navigation menus, or formatting rules. In practice, it is a general mechanism for modular content assembly across many platforms.

Benefits include reduced duplication, a single point of update, and greater consistency across documents. It supports modular design and reuse. Challenges include performance overhead, caching that may diverge from source, potential for circular dependencies, versioning conflicts, and security considerations when including remote or user-provided content.

Related concepts include templating, server-side includes, and dynamic content loading.