A SOAP request to, or response from, a service is generated according to the service’s WSDL definition. A WSDL document describes a service. It is an XML document that provides information about what the service does, the methods that are available, their parameters, and parameter types. It describes how to communicate with the service in order to generate a request to, or decipher a response from, the service.

The purpose of a WSDL is to completely describe a Web Service to a client. A WSDL defines where the service is available and what communications protocol is used to talk to the service. It defines everything required to write a program to work with an XML Web Service. A WSDL document describes a Web Service using seven major elements. Elements can be abstract or concrete.

Abstract XML elements describe the Web Service: <types>, <message>, <operation>, <portType>.

Concrete XML elements provide connection details: <service>, <port>, <binding>.