erver's access control mechanisms, while a Responder that takes the
name of a data file as a parameter must perform its own access control
checks on the data file.<p>

The steps taken by a Filter are similar to those of a Responder.
The server presents the Filter with environment variables first,
then standard input (normally form <tt>POST</tt> data), finally
the data file input:<p>
<ul type=square>
    <li>
        Like a Responder, the Filter application receives name-value
        pairs from the Web serv