About SOAP invocation messages

SOAP is a protocol for exchanging XML-based messages over a network, and is used for sending messages between web services and their clients. Client software sends SOAP messages to web services to invoke web service operations. Web services return the operation results to clients using another SOAP message.

The XML that represents a SOAP message that is sent to invoke a web service operation is comprised of the message envelope, header, and body:

Envelope:: The Envelope element is the root element of the XML document that represents the SOAP message. This element contains the message header and body.
Header:: The Header element contains information that is not directly related to the web service operation. This element serves as a mechanism for providing information to the software that processes the message. For example, the header is typically used to transfer user credentials for authentication reasons. It is optional to include the Header element unless the web service requires it.
Body:: The Body element contains one element that represents a call to the web service operation that is being invoked. The element type is the name of the operation. The operation element contains elements that represent the operation parameters. These element types are the names of the parameters, and contain the parameter values.
The name of the web service operations, as well as the parameter names and data types are defined in the web service definition. Most web service clients retrieve and interpret the definition automatically.

Namespaces

The Envelope element must be prefixed with a namespace alias whose declaration uses "http://schemas.xmlsoap.org/soap/envelope/" as the namespace identifier. If the following namespace declaration is used for this namespace, the Header element is prefixed with soapenv:

xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"

Other namespaces that are declared are namespaces that the web service definition defines. These namespaces are used to prefix the XML elements that are associated with the web service operation. For example, web services for invoking activated processes use the namespace identifier "http://adobe.com/idp/services" .

Example

The following XML code is an example SOAP message element that represents a call to the web service’s operation named operation_name. The operation takes one parameter named parameter_name.

<soapenv:Envelope  
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://foo.net/services"> 
    <soapenv:Header /> 
    <soapenv:Body> 
        <ser:operation_name> 
            <ser:parameter_name>?</ser:parameter_name> 
        </ser:operation_name> 
    </soapenv:Body> 
</soapenv:Envelope>