A wiki overlay could, like a stacking filesystem, read pages from two wiki instances but direct all write operations to the "top" wiki.
This way a group of pupils could be given their own instance and work on their own copy of an initial state from the "bottom" wiki. The initial state could, for instance, contain goals, tasks and content that asked for reorganization. Different groups of pupils (e.g. classes or grades) could be given the same initial state and develop it in their own wiki instance in different ways.
The reorganization work could, for instance, be equivalent to, accompany or lead to a book project.
A different use of a Wiki overlay could be for correcting a text written by pupils. The overlay could contain the markup and annotations made by the tutor/teacher.
- The wiki software could reformat text when storing an edit: Where possible sentences should be put in a single line, without line breaks in the sentence and a reliable line break at the end, which would improve the readability of differences between versions.
- Technical ideas for wikis (meta.wikimedia.org)