code: @Override
  	public int getPropagationConditions(int vIdx) {
  		if (vIdx == 0) {
  			return SetEventType.ADD_TO_KER.getMask() + SetEventType.REMOVE_FROM_ENVELOPE.getMask();
  		} else {
  			return GraphEventType.ADD_ARC.getMask() + GraphEventType.REMOVE_ARC.getMask();
  		}
  	}
docs: ***********************************************************************************