[scofalik]

Our first idea was to have four basic operations (insert, move, attribute, remove) and then have “deltas” (wrap delta, unwrap delta, merge delta, split delta) which were built using those operations and for which we described additional transformation cases. In this approach operation transformations were set in stone, but you could add your own deltas and provide your own transformations for them.

In the end, we concluded that users will see defining deltas and transformations as too complicated and won’t use it. Later, we also decided to drop deltas idea at all and we rewrote deltas into operations.

As an alternative solution, we provide the post-fixing mechanism. Your plugin can listen to all the changes done on the model and apply fixes if something has gone wrong. We used it for the famous "insert table row / insert table column" problem, to add the missing cell. This alternative is not as clean as explicitly providing a transformation algorithm but it is much easier to implement.

The problem with defining your own operations is that you need to write transformations against all the other operations which is a huuuuge work. It took as a few years and we still see some room for improvement.