By Dan Kozin, Director, Product Management, Vision Server Products
The World Wide Web Consortium (W3C) defines Call Control eXtensible Markup language (CCXML) as a developing standard for managing and supporting telephony call control with a VoiceXML-based application. While it is designed to be used with any media capable dialog application, CCXML’s key benefit is the ability to complement and integrate with VoiceXML to setup, monitor, and tear down phone calls.
Because VoiceXML was designed to support a simple transactional-based single-threaded programming model and telephony call control requires a more complicated asynchronous event handling model, a different standard was needed. CCXML was created to support an event-based model that could receive and respond to multiple asynchronous events while being compatible with VoiceXML.
VoiceXML was designed for media presentation in a call, it uses a linear approach. This model works well within user-interface-supplied commands, but does not provide an easy way to operate outside a pre-determined set of options. For example, a call center application that intelligently gathers information from the caller, and then passes that information on to the call center agent before answering the call, benefits from CCXML by easing the information flow within the call.
With these two open standards, media application developers can leverage the strength of web platforms and technologies to intelligently control calls on and off the telephone network.
CCXML was designed with these goals in mind:
- Support for multi-party conferencing, with more advanced conference and audio control.
- Sophisticated multiple-call handling and control, including the ability to place outgoing calls at any time, initiated outside of the VoiceXML platform.
- Handling for richer and more asynchronous events. Advanced telephony operations involve substantial signaling, status events, and message-passing. VoiceXML does not currently have a way to integrate these asynchronous "external" events into its event-processing model.
- An ability to receive events and messages from systems outside of the CCXML or VoiceXML platform. Interaction with an outside call center platform, calls started asynchronously from the VoiceXML platform, and communication between multiple "clustered" VoiceXML or CCXML platforms all require event interaction from one XML platform to another.
CCXML provides the following functionality not possible with VoiceXML alone:
- Routing: Routes calls to the next available line in a group; or find me/follow me capability to track a person down at multiple possible locations.
- Bridging: Connects a call between two call legs.
- Outbound Calling: Initiates a call and starts one or more VoiceXML dialogs once a connection is established.
- Selective Call Answering: Decides whether or not to answer a call based upon caller information.
- Conferencing: Allows multiple participants to join a phone conference.
- Coaching: Allows a third party to connect to a call, but only have one of the participants hear what is said.
- Dialog Execution: New instances of VoiceXML interpreters can be created and destroyed at will.
Figure 5 shows how CCXML and VoiceXML work together (source: http://www.developer.com/voice/article.php/1565751):
Remember, CCXML is not a media/dialog language like VoiceXML. It only provides support to move calls around and connect them to dialog resources.
NMS has chosen to add CCXML 1.0 support in its next release of the Vision VoiceXML Server to provide a complete application-ready platform that can deliver interactive voice and video applications by using markup languages such as VoiceXML 2.0 and 2.1, and CCXML 1.0. NMS’s Vision VoiceXML Server provides operators and value-added solutions providers the ability to rapidly develop and deploy new and innovative voice and video applications for IP, PSTN, and 3G-324M networks. Applications that are well suited for VoiceXML and CCXML interpreters include voice and video messaging, speech enabled IVVR systems, and interactive entertainment.