Call Control Work Progressing Quickly in the W3C

By Brad Porter

VoiceXML spread like wildfire in 2001. VoiceXML extends the reach and effectiveness of the Web by allowing interactivity and information delivery using voice. VoiceXML can be used to deliver customer service
efficiently and inexpensively, just as companies now use HTML to deliver information quickly and cheaply.

By combining voice recognition and dialog flow in a simple XML-based language, VoiceXML is revolutionizing the industry. However, in order to build applications that move the caller across a telephony network, call control is necessary.

VoiceXML 1.0 assumed a simple call model where the call arrived to the VoiceXML platform over a traditional telephony line and could perform a bridged or blind transfer to a 3rd party. The good news is that those features alone cover a huge range of applications in production today! The bad news is that VoiceXML was not cleanly extensible for outbound calls placed by the platform, new call control features, or new telephony networks. For instance, in VoiceXML the transfer tag does not permit the application to play audio during the transfer, for instance "you have 30 seconds left on this call".

The W3C Voice Browser working group has been working hard since January of 2001 to address these limitations head-on. We've focused explicitly on supporting different telephony networks, outbound calls, and new call control capabilities.

We have redefined the call model in terms of a connection object. The connection object is agnostic to whether the call was originated by the caller or the platform. The connection object generalizes
core connection attributes such as the remote caller's address and the local platform's address.f The connection object also incorporates a protocol-extensible object space allowing for detailed
representation of the attributes of any connection protocol.

We have completed the first cut of the connection object and are in the process of incorporating it into the next draft of VoiceXML 2.0. This will replace the existing session.telephone variable space with the new
connection object exposed at the session level in VoiceXML. Similarly, we've replaced the weakly-defined telephony addressing schemes in VoiceXML with standard URI schemes such as tel: URI's and sip: URI's.

Many VoiceXML platform vendors already support the ability to place outbound calls. Now that the VoiceXML 2.0 language call model is agnostic to whether the call was placed by the platform or arrived from the caller, we need a standard way to request that a platform place an outbound call. We are working on completing proposals that will allow this.

The most ambitious project is the new CCXML specification. In late 2000 and early 2001, a group of companies including Tellme, Intel, Cisco, Telera, and Voxeo began working on an XML markup language which enables advanced call control features on any telephony network. After thorough review of the architectural options, the W3C working group decided to adopt their initial work as the foundation for our work in advanced call control capabilities.

All this foundation work will enable the next generation of telephony services such as conferencing, enhanced transfer, and find-me-follow-me applications to be built upon Internet standards!

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