This special Modification notifies the fulfillment system of any changes within a Shipping Group that happen externally. If the OrderFulfiller receives a ModifyOrderNotification with a ShippingGroupUpdate Modification in it, the shipping groups listed in the Modification are reprocessed.

This is a convenient way of notifying fulfillment of complex changes to an order. It contains an order ID and an array of shipping group IDs that have been updated. After receiving this message, the OrderFulfiller forwards it to each of the appropriate fulfillers, who then reprocess the entire shipping group.