无法确定＆＃39; XSD的命名空间：STRING＆＃39;

Question

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tns="http://mobicash_branded/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://schemas.xmlsoap.org/wsdl/" targetNamespace="http://mobicash_branded/" name="MobicashService">
    <types>
        <xsd:schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:Mobicash">
            <!--<xsd:import namespace="http://mobicash_branded/" schemaLocation="http://192.168.68.11:23555/mobicash/soap.wsdl"></xsd:import>-->
        </xsd:schema>
    </types>
    <message name="send_messageRequest">
        <part name="action" type="XSD:STRING"></part>
        <part name="username" type="XSD:STRING"></part>
        <part name="password" type="XSD:STRING"></part>
        <part name="receiver" type="XSD:STRING"></part>
        <part name="msgdata" type="XSD:STRING"></part>
        <part name="senttime" type="XSD:STRING"></part>
        <part name="rrn" type="XSD:STRING"></part>
    </message>

    <message name="send_messageResponse">
        <part name="result" type="tns:ArrayOfString"/>
    </message>
    <portType name="Mobicash">
        <operation name="send_message">
            <input message="tns:send_messageRequest"></input>
            <output message="tns:send_messageResponse"></output>
        </operation>
    </portType>

    <binding name="MobicashPortBinding" type="tns:Mobicash">
        <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document"></soap:binding>
        <operation name="send_message">
            <soap:operation soapAction=""></soap:operation>
            <input>
                <soap:body use="literal"></soap:body>
            </input>
            <output>
                <soap:body use="literal"></soap:body>
            </output>
        </operation>
    </binding>
<service name="MobicashService">
    <port name="MobicashPort" binding="tns:MobicashPortBinding">
        <soap:address location="http://192.168.68.11:23555/mobicash/server.php"></soap:address>
    </port>
</service>
</definitions>

每当我们使用SOAPUI Client使用上述服务时，我们都会收到以下错误：

faultCode=UNBOUND_PREFIX: Unable to determine namespace of 'XSD:STRING'.

上面提到的服务是用PHP编写的，我们正在尝试使用java / ASP.NET消费该Web服务