The next element, operation, is perhaps the easiest of all the WSDL elements to understand. An operation is, as its name pretty clearly suggests, a parallel to a Java method. There are several key differences, of course. One of them is that an operation has three and only three messages. They are:
This isn't a great stretch from Java methods. After all, a Java method has only one return object, and it is not uncommon for a method to throw only one type of exception. The main difference here lies in the fact that an operation has just one input message, rather than a list of input parameters.
Operations generally fall into four forms, based on the nature of the communication. ...