A change made to a version checked out in the scope of an activity can be reverted using an operation called 'Uncheck out'.
The following figure shows the starting point.
Version 1 has been checked out for edit. It's still the active version in the workspace. Version 2 exists as an open version, associated with activity X.
If the user decides to discard/revert the version 2 created in the scope of activity X , the state of the workspace goes back to its former state as shown in the following figure.
Version 2 has been discarded by the uncheck-out operation. The workspace is in its former state.