An Accept Change Structural Feature Event Action is an action that waits for the occurrence of a Change Structural Feature Event (see Directed Feature). The actions have exactly two output pins. The first output pin holds the values of the structural feature just after the values changed, while the second pin holds the values just before the values changed. The action only accepts events for structural features on the blocks owning the behavior containing the Action, or on the behavior itself, if the behavior is not owned by a Block.