确定架构风味 - 寻找奇迹

Question

知道是什么引发了这个错误吗？

数据中的语法错误：无法从根元素“PurchaseOrders in PurchaseOrders”中确定架构风格

<?xml version="1.0" encoding="UTF-8"?>
<ns0:PurchaseOrders xmlns:ns0="PurchaseOrders">
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
 elementFormDefault="qualified"
 attributeFormDefault="unqualified">
<xs:element name="PurchaseOrderCount" type="xs:byte"/>
<xs:element name="TransmissionID" type="xs:string"/>
<xs:element name="SenderID" type="xs:string"/>
<xs:element name="ReceiverID" type="xs:string"/>
<xs:element name="TimeStamp" type="xs:string"/>


end of file

    <xs:element ref="OrderDetail"/>
        </xs:sequence>
    </xs:complexType>
</xs:element>
</xs:schema>
</ns0:PurchaseOrders>