There are two ways to track the changes being made by the user:
(Requries Version 3.6)
Track Changes
$forms->trackChanges = true;
Will store all changes being made in the array $forms->changes. The typical usecase is in combination with an post-update handler where you send all changes to a certain email address.
Revisions / History / Version control
$forms->storeRevions = true;
Will create a second table like the current table in use. After each update, the old data set will be store in the second table with the date of the update so you can see all versions that ever existed. Changes to file and foreign sets are not stored yet.
Sample Code
Live Sample