ys one of several well-defined <i>roles</i>.
The most familiar is the <i>Responder</i> role, in which the
application receives all the information associated with an HTTP
request and generates an HTTP response; that's the role CGI/1.1
programs play.  A second role is <i>Authorizer</i>, in which the
application receives all the information associated with an HTTP
request and generates an authorized/unauthorized decision.
A third role is <i>Filter</i>, in which the
application receives all the information ass