In the full description of the exercise, the author write that the WebService object handles the WSDL document with dynamic data for the client application. Actually, the WSDL (Web Services Description Language) is a XML-based language that provides a model for describing Web Services. Is is used by Flex framework to generate an object proxy to consume the Web Service transparently from the client. The WSDL document does not transport dynamic data for the application. The SOAP (Simple Object Access Protocol) describes the XML message format and the protocol to transport the dynamic data, not the WSDL document.