invoice.xml

<?xml version="1.0" encoding="UTF-8"?>
<dat:dataPack>
  <dat:dataPackItem>
    <inv:invoice>
      <inv:invoiceHeader>
        <inv:invoiceType>issuedInvoice</inv:invoiceType>
      </inv:invoiceHeader>
      <inv:invoiceDetail>
        <inv:invoiceItem>
          <inv:text>some item</inv:text>
        </inv:invoiceItem>
        <inv:invoiceItem>
          <inv:text>some other item</inv:text>
        </inv:invoiceItem>
      </inv:invoiceDetail>
    </inv:invoice>
  </dat:dataPackItem>
</dat:dataPack>