In WSDL 2.0 there is the option to leave out operation-specific information in a binding.
In fact, it is possible to omit even the interface to which the binding is to apply to, in order to enable the binding to be used at multiple occasions.
In your example, however, both interface and an operation are supplied, so this is a binding that cannot be reused.
The input and output elements of the "binding component" (as it is called in WSDL 2.0) are optional.
If not defined, the the default options specified in the binding component are to be used. I thus expect all the operations in the example you provided to use SOAP 1.1 over HTTP, as specified in the <wsdl:binding> element.