In Knowen all edits are sequential. The goal is to avoid editing conflicts, complex issues with merging multiple versions, and, finally, to have a complete attributable historical record of all changes.
When page is being edited by an author, all other users will see (recall) next to Edit page button to indicate that the pages is being edited.
Clicking on "Edit page" gives an option to recall editing from the current author. If one finds that the page has been "checked out" for extended period of time, the chances are that the current author simply forgot about it, or the page remained checked out do to a computer crash, etc. In this case recalling page is justified.
Upon recall, the current author is given a notification that the page will be released in 10 minutes automatically. This gives the author enough time to commit their changes. Alternatively, they can release the page without committing. Whether the author releases the page, or the pages is released automatically, all uncommitted changes are preserved as a draft, available to the author when they open the page for editing the next time.
After the page has been released, either the recaller or any other author can start editing it.