Programming Internet telephony services

The Internet offers an opportunity to enhance traditional telephony services, such as call forwarding, through interaction with e-mail, the Web, and directory services, as well as traditional media types. How do you effectively program these services? The authors propose a CGI (common gateway interface) solution for trusted user/developers (such as administrators) and the Call Processing Language (CPL)-a simple, robust, safe, call processing language-for untrusted user/developers.