A Unified XML integrated voice and data application delivery system includes a switch coupled to a first network and at least a second network, wherein the first network includes distinct voice and data applications and the second network includes one or more user devices, such as a cell phone, personal digital assistant (PDA), etc. The switch transfers voice and data between the applications and the user devices. A controller coupled to the switch includes a finite state machine controlling the interaction between the voice and data applications and the user devices. The finite state machine controls the transfer of voice and data between the applications and the user devices by the switch to enable a user to interact with the integrated instance of the voice and data applications simultaneously via the user devices. The second network includes data networks such as the Internet, wireless networks, and the public switched telephone network, and the user devices can include telephones, cell phones, personal digital assistants (PDAs) and other devices. A Unified XML engine governs the management and delivery of disparate XML files and RTP streams of converged voice and data content to heterogeneous devices over disparate carrier networks and protocols.