The CGI programs

As has been mentioned before, World Wide Web servers are able to adress external programs via the CGI. The call of a CGI program is usually initiated by activating a hyperlink that was found in a HTML document previously transferred to the client side. Since the activities of the CGI programs are well defined within the web scenario for each state of the protocol between sender and receiver, separate CGI programs were defined for each state.

Both CGI calls during the authentication phase are performing identical tasks with regard to Plasma, they do, however, send different web pages as a response to the client.

The CGI program called during document transfer gets the requested document and decides whether or not the client has access to the requested document by means of the embedded client DName . Lastly, there is a separate CGI program which gets called if a request for terminating the session with the client is detected.

All CGI programs are searching for the Plasma identification string and passing as the proxy on client side these data onto Plasma.

  

Figure: The interactions in the authentication phase