What is a feature-binding?

ref:
http://www.w3.org/TR/2004/WD-wsdl20-extensions-20040803/#adf-http-serial

"3.3 Application data serialization as HTTP headers
3.3.1 Name

This feature-binding is identified with the URI
'http://www.w3.org/2004/08/wsdl/feature/AD-HTTP'"

Part 2 introduces a new concept, feature-binding. This is in addition to
Features and SOAP Modules. What is a feature-binding? Please clarify.

Regards,
Asir S Vedamuthu
asirv at webmethods dot com
http://www.webmethods.com/