Call Processing Language (CPL) is a language that can be used to describe and control Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 telephony

Telephony

In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....

 services. It is designed to be implementable on either network servers or user agent

User agent

In computing, a user agent is a client application implementing a network protocol used in communications within a client–server distributed computing system...

 servers. It is meant to be simple, extensible, easily edited by graphical clients, and independent of operating system or signaling protocol

Signaling protocol

A signaling protocol is a type of protocol used to identify signaling encapsulation. Signaling is used to identify the state of connection between telephones or VOIP terminals . The following is a list of signaling protocols:...

. It is suitable for running on a server where users may not be allowed to execute arbitrary programs, as it has no variables, loops, or ability to run external programs.

Sources

• coverpages

In Case of Session Initiation Protocol Servers(SIP servers),it can be used to specify the
user defined preferences like
(please refer to the rfc3880 for further details)

1)Authenticate calls To And From The user
based on

Address Info -callerid
-domain of caller
-domain of callee
-display name of caller/callee

DateTime of call

-day of call
-hour of call
-minute of call
-year of call

language preferences

priority over subscribed numbers

2) modification of user locations in server through UI

3) Call routing logic

-how long to ring a phone
before doing further action
based on the result of the call

like --busy
--noanswer
--notfound
and then take appropriate
action
etc....
etc...