confued about operation mapping

In XI7.10, each service interface can have multiple operations, for example: the service interface PurchaseOrderProcessingOrderingOut in namespace http://sap.com/xi/AP/Purchasing/Global and Software Component Version SAP AP 7.10 has three operations:

RequestPurchaseOrderCancellation, RequestPurchaseOrderChange and RequestPurchaseOrderCreation. Each opeartion has different message types.

Now I have three operation mappings for each operation, let's name them A, B and C.

I have an interface determination. The sender business system is xxx_bs, the sender interface is PurchaseOrderProcessingOrderingOut, the receiver business system is yyyy_bs. In this interface determination, I choose operation mapping A for the operation RequestPurchaseOrderCancellation, operation mapping B for the operation RequestPurchaseOrderChange, and operation mapping C for the operation RequestPurchaseOrderCreation.

Now the problem is: in the XI-SOAP envelope, there is only information about sender service: xxx_bs, sender interface: PurchaseOrderProcessingOrderingOut and its namespace. How can XI know the operation is RequestPurchaseOrderCancellation, or RequestPurchaseOrderChange or RequestPurchaseOrderCreation, and then determines which opeartion mapping to use in the Interface Determination step.

Best Regards,

Annie