In Forms 10.4.2 you can now select to Skip or Interrupt an activity. I know that you cannot use Interrupt on a Gateway, but besides that what is the difference between the two?
The difference between interrupt and skip is: after skip a step, the instance will always go to the next step; after interrupt a step, the instance won't go to the next step, it will treat the interrupted step as an end step, if the step is the only active step in the instance, the instance will become completed. The purpose interrupt is added is to solve following situation: If "User Task 1" is completed and "Parallel Gateway (1)" is skipped, the instance run to "User Task 3" but "User Task 2" is still in progress, if user skip "User Task 2", the instance will run to "Parallel Gateway (1)" again, and if user skip "Parallel Gateway (1)" again, the instance will run to "User Task 3" again, this will make "User Task 3" execute multiple times. To avoid this issue, user should interrupt "User Task" instead, then the instance won't go to "Parallel Gateway (1)" again and "User Task 3" will only be executed one time.