Types describe all the data types used between the client and server.
WSDL is not tied exclusively to a specific typing system, but it uses the
W3C XML Schema specification as its default choice.
WSDL allows type systems to be added via extensibility elements.
An extensibility element may appear under the types element to identify
the type definition system being used and to provide an XML container element
for the type definitions.
To add an XSD type or element to your WSDL
In the Design view, click the arrow icon to the right of the port
type object to open that operation in the XML schema editor.