Basic Web Services Workflow
There is a fundamental workflow involved with the description, discovery, and integration of Web services. Understanding this flow is important to appreciate the security concerns I will address later in the article.
Develops a service (usually a function/procedure or method that may link through several classes and components) in his own language and environment.
Develops a SOAP layer over and above the service, so that the service can be exposed to SOAP method calls across the Web. In other words, a simple service has become a "Web service."
Develops a WSDL file, which contains the details of the service, input/output parameters, and so on.
Publishes his service with a service directory system such as UDDI.
Negotiates with the service provider to make use of his service.
Downloads the WSDL file from the service directory, and understands the details of service invocation.
Develops a client program that will make use of the service.
Develops a SOAP layer over the client program so that SOAP calls can be sent and received across the Web. In other words, a simple client has become a Web service client.
Invokes the service with a SOAP call, as and when required.
This entire flow is illustrated in Figure 1.
Figure 1 Web services workflow.