Messages represent an abstract definition of the data being transmitted. A message consists of logical parts, each of which is associated with a definition within some type system. WSDL messages are top level objects that can be referenced by an operation's input, output and fault elements (within a port type).
Note: Changes of service elements are not automatically propagated to bindings. You need to regenerate the binding content and select the Overwrite existing binding information check box in the binding wizard to reflect changes in the WSDL. For more information, see Setting a binding.