To put it simply: The framework expresses an upgrade and an downgrade path for a type:
Upgrade("TypeName") -> List
Downgrade("TypeName") -> List
The backup and sync provider can use this list to perform the real actions on the datastore. Of course this methods don't exist because real world upgrade scenarios are more complex. I will publish the real API on first release.
The project will be hosted on CodePlex, open source, GPL licensed and is currently in setup state. Hiere is the Project: MSE-iT Upgrade Framework on CodePlex But for the moment, it is not published. I will post when i check in the initial development.