Definition of a proxy firewall

[Don Ng]

Hi all, I have been selling firewall recently and I would like to know what constitutes a more formal definition of a "proxy application firewall".  I do know that there is no single clear description but probably various degrees of "proxiness" <is that a word?>    Could anyone care to rehash an old debate? I have only been exposed to CyberGuard and Cisco pix firewalls,at this point in time so limited vision.   Proxy 1.0 Act as a middleman 2.0 Traditional client to server becomes client to FW to Server and in the reverse direction. 3.0 Supposed to follow RFC on protocol standards <which, how much> 4.0 Supposed to be able to filter on commands at the application level.     Nothing too heated please.   Don Ng