运行简单转换时出现 Ref-Node 错误

我在使用简单转换时遇到一个问题，我无法弄清楚。

CX_ST_REF_ACCESS运行代码在转换行上给我以下错误消息（异常类） <tt:loop name="PurchaseOrder" ref="PurchaseOrder">：

访问引用节点“PURCHASEORDER”时出错。引用节点未定义或没有必要的类型

当我使用时出现错误CALL Transformation。

我尝试使用简单转换从 XML 中读取数据。

这是我的简单转变：

<?sap.transform simple?>
<tt:transform xmlns:tt="http://www.sap.com/transformation-templates">
  <tt:root name="PurchaseOrder"/>

  <!-- Root element: PurchaseOrder -->
  <tt:template>
    <tt:loop name="PurchaseOrder" ref="PurchaseOrder">
      <PurchaseOrder>

        <!-- Address Elements -->
        <Address>
          <tt:loop name="Adress" ref="PurchaseOrder.Address">
            <Name>
              <tt:value ref="Name"/>
            </Name>
            <Street>
              <tt:value ref="Street"/>
            </Street>
            <City>
              <tt:value ref="City"/>
            </City>
            <State>
              <tt:value ref="State"/>
            </State>
            <Zip>
              <tt:value ref="Zip"/>
            </Zip>
            <Country>
              <tt:value ref="Country"/>
            </Country>
          </tt:loop>
        </Address>


        <!-- DeliveryNotes Element -->
        <DeliveryNotes>
          <tt:value ref="PurchaseOrder"/>
        </DeliveryNotes>

        <!-- Items Section -->
        <Items>
          <tt:loop ref="PurchaseOrder">
            <Item>
              <ProductName>
                <tt:value ref="ProductName"/>
              </ProductName>
              <Quantity>
                <tt:value ref="Quantity"/>
              </Quantity>
              <USPrice>
                <tt:value ref="USPrice"/>
              </USPrice>
              <tt:cond>
                <Comment>
                  <tt:value ref="Comment"/>
                </Comment>
              </tt:cond>
              <tt:cond>
                <ShipDate>
                  <tt:value ref="ShipDate"/>
                </ShipDate>
              </tt:cond>
            </Item>
          </tt:loop>
        </Items>
      </PurchaseOrder>
    </tt:loop>
  </tt:template>
</tt:transform>

我的 ABAP 代码（精简到相关部分）：

TYPES: BEGIN OF ty_address,
         name    TYPE string,
         street  TYPE string,
         city    TYPE string,
         state   TYPE string,
         zip     TYPE string,
         country TYPE string,
       END OF ty_address.

TYPES: BEGIN OF ty_item,
         productname TYPE string,
         quantity    TYPE i,
         usprice     TYPE p DECIMALS 2,
         comment     TYPE string,   " Optionales Feld für Kommentar
         shipdate    TYPE d,        " Optionales Feld für ShipDate
       END OF ty_item.

DATA: BEGIN OF ty_purchase_order,
         addresses     TYPE TABLE OF ty_address, " Mehrere Address-Einträge
         deliverynotes TYPE string,
         items         TYPE TABLE OF ty_item,    " Tabelle mit Items
       END OF ty_purchase_order.

DATA: gv_file       TYPE string,              " Datei für den Upload
      lt_xml_table  TYPE TABLE OF string,     " Tabelle für XML-Zeilen
      gv_xml_string TYPE string.              " Für das gesamte XML als String

gv_file = p_file.
CALL METHOD cl_gui_frontend_services=>gui_upload
  EXPORTING
    filename                = gv_file
*   codepage                = '1252'
  CHANGING
    data_tab                = lt_xml_table
  EXCEPTIONS
    file_open_error         = 1
    file_read_error         = 2
    no_batch                = 3
    gui_refuse_filetransfer = 4
    invalid_type            = 5
    no_authority            = 6
    unknown_error           = 7
    bad_data_format         = 8
    header_not_allowed      = 9
    separator_not_allowed   = 10
    header_too_long         = 11
    unknown_dp_error        = 12
    access_denied           = 13
    dp_out_of_memory        = 14
    disk_full               = 15
    dp_timeout              = 16
    not_supported_by_gui    = 17
    error_no_gui            = 18
    OTHERS                  = 19.

LOOP AT lt_xml_table INTO DATA(lv_line).
  CONCATENATE gv_xml_string lv_line INTO gv_xml_string.
ENDLOOP.

CALL TRANSFORMATION ZJB_TRAN0
SOURCE XML gv_xml_string
RESULT PurchaseOrder = ty_purchase_order.

最后我想要处理的 XML 文件是：

<PurchaseOrder>
<Address>
<Name>Ellen Adams</Name>
<Street>123 Maple Street</Street>
<City>Mill Valley</City>
<State>CA</State>
<Zip>10999</Zip>
<Country>USA</Country>
</Address>
<Address>
<Name>Tai Yee</Name>
<Street>8 Oak Avenue</Street>
<City>Old Town</City>
<State>PA</State>
<Zip>95819</Zip>
<Country>USA</Country>
</Address>
<DeliveryNotes>Please leave packages in shed by driveway.</DeliveryNotes>
<Items>
<Item>
<ProductName>Lawnmower</ProductName>
<Quantity>1</Quantity>
<USPrice>148.95</USPrice>
<Comment>Confirm this is electric</Comment>
</Item>
<Item>
<ProductName>Baby Monitor</ProductName>
<Quantity>2</Quantity>
<USPrice>39.98</USPrice>
<ShipDate>1999-05-21</ShipDate>
</Item>
</Items>
</PurchaseOrder>