Storing information within the page revision content, has the following benefits:
* Part of page history, comparable and reversible together with other related content.
* Editable by users at the same time as other content, and allows them to make a single atomic change.
We currently do this for categories, infoboxes and template data. But embedding this in wikitext has downsides. While it is possible to extract data via the Parser (as for categories), invoking the Parser has a cost. For that reason, we actually store some of the derived data in link tables, but that is only available for the current revision. The goal of MCR is to allow accessing individual slots of content without the overhead of the parser.
Other data is currently stored outside wikitext, such as template documentation, quality assessment, and more. MCR would allow bringing these into the subject page.
The idea of this RFC is to allow multiple `Content` objects to be associated with a single revision. A revision will have multiple slots, and each slot can be occupied by one Content object. The "main" slot being reserved for the primary content of the page (that is, for what is currently considered the content of the page).
For details, see **[[https://www.mediawiki.org/wiki/Multi-Content_Revisions|the MCR design document on mediawiki.org]]**.