Canceling alerts, tasks, or notifications
Sometimes, you must cancel an alert, task, or notification before the user handled it. For example, a requisition approval task is created, but now the requestor cancels the requisition. In this case you must also cancel the task in the Activities engine.
This diagram shows a task (PulseTask), but the process is the
      same for notifications and alerts.
    
If you created a task by sending a ProcessPulseTask with action
      code 'Add', you receive an AcknowledgePulseTask which contains the ID of the
      task. You can use this ID to send a new ProcessPulseTask request to cancel
      the task.