Like in Wiki, there are two kinds of edits:
1. Versioned edits 2. Minor edits
Minor edits do not create new versions of the document, but change existing version instead. As such, they are irreversible. Only latest version can be edited.
It is author's decision, wether to designate change as minor or as versioned.
When a new version is created, all objects linking to this one are notified. Their action can be one of the following: