This images shows the following:

• Invoice and P.O. are datatypes.
• The invoice line items are mapped to the P.O. items.
• The invoice line items and the P.O. items are datatype members with multiple occurrences.
• Iid, qty, cost, and identifier, quantity, and cost are datatype members with a maximum cardinality of one.
• The line item id is mapped within an invoked map to the P.O. item identifier.
• The line item qty is mapped within an invoked map to the P.O. item quantify.
• The line item cost is mapped within an invoked map to the P.O. item cost.