X-eye principle (e.g. four-eye principle)

$T1:=OrderBookGetTask[OrderBookTaskReleaseRequired];
$T1 and $T1

The function OrderBookGetTask function creates a task object of a specific type, which is passed as a parameter. The type OrderBookTaskReleaseRequired ("User release required") is supplied here. The resulting task then requires approval by a user. The task can be logically linked to itself or to other task objects. In this example, this task has to be performed twice ("and" link), which corresponds to a four-eye principle.