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[April 23, 2002]

Beyond VoiceXML: Standardizing Call Control Capabilities Through CCXML


It has been a whirlwind two years for the organizations that have worked diligently to standardize the methods of creating speech-enabled applications. In early 2001, the World Wide Web Consortium (W3C) adopted VoiceXML as a markup language for creating speech applications such as self-service, voice portals, and voice-enabled dialing. Shortly thereafter, the Voice Browser Working Group (VBWG) -- a W3C working group dedicated to evolving VoiceXML -- began working on the VoiceXML 2.0 specification; they released the first public working draft in October 2001.

As developers and the voice industry started adopting VoiceXML, many found that the standard wasn't robust enough to meet their needs. While VoiceXML has well-rounded dialog interaction capabilities, it lacks the call control functionality that is critical in many enterprise applications, such as those deployed in contact centers.

This discovery led several members of the VBWG to propose a separate markup language that would define the specification for call control capabilities. That standard is Call Control eXtensible Markup Language (CCXML), and it picks up where VoiceXML leaves off in terms of call control functionality. The VBWG released the first public working draft in January 2002.

Unlike VoiceXML, which is designed primarily to serve voice dialogs between the user and the computer, CCXML offers sophisticated call-handling capabilities and complex telephony applications such as multi-party conferencing and interactive voice response on multiple call legs (dedicated communication paths between either two callers or a caller and a speech-enabled application). CCXML provides unique benefits for enterprises, service providers, and developers that are taking advantage of the latest advancements in speech-enabled technology.

Extending The Capabilities Of VoiceXML
The current VoiceXML specification includes rudimentary call transfer capabilities but has some limitations. For example, it does not have the features required to control outbound call legs. VoiceXML allows an application to transfer a caller to another person, however, once the call is transferred, the application terminates. The caller does not have the ability to loop back to the application; instead, they would have to call the application back.

There are other limitations in the current VoiceXML specification:

  • Applications can't control the outbound call leg once a call is transferred.
  • The standard does not facilitate the initiation of a dialog session or voice user interface on a transferred call leg.
  • VoiceXML does not support conferencing capabilities where multiple callers can talk to each other at the same time.
  • VoiceXML cannot support the development of many essential contact center applications such as whispering (providing the data a caller enters to an agent prior to call transfer) or supervised transfer (in which agents can put callers on hold and introduce them prior to transferring to other agents).

CCXML is designed to overcome these limitations but does not replace VoiceXML. Instead, the two standards complement each other to provide the best elements of application development with VoiceXML, and essential call control functionality with CCXML. Therefore, developers can write applications that are usable, conversational, and meet enterprise contact center needs. The combination of CCXML with VoiceXML makes speech applications enterprise-ready.

CCXML Features
With CCXML, developers can enhance their voice applications with the following call control capabilities (and more), which provide a personalized application experience that will increase the adoption of speech-enabled applications:

  • Control multiple call legs: Developers can place multiple outbound calls and control each outbound call leg independently. Each call may optionally provide voice dialog interaction.
  • Event handling: The ability to handle asynchronous events that come from telephony infrastructure and the VoiceXML Interpreter.
  • Start and stop an IVR session: Developers have complete control over initiating and terminating IVR sessions that are executed in a VoiceXML Interpreter.
  • Conditional logic: Similar to VoiceXML applications, CCXML applications can use conditional elements to implement the business logic.
  • Web server interaction: Communicate with Web servers using HTTP to retrieve documents.

With the advanced features of CCXML, developers can create applications that involve complex telephony and dialog interaction. There are several user scenarios where CCXML is a natural choice for developers, including find-me/follow-me applications and multi-party conferencing (see table below).

User Scenario Description
Find-me/follow-me applications Find-me/follow-me applications allow users to be reached at one of several locations by a single number. Users benefit from using a single number and callers memorize several numbers.
Agent re-transfer In this scenario, contact center agents can transfer callers to other agents multiple times. Applications can use the DTMF input collected from either call leg (caller or recipient) to determine its origin and handle calls appropriately.
Supervised transfer In a supervised transfer, agents can put callers on hold and introduce them prior to transferring the call to other agents. Such introductions enable personalized customer support and improve the user experience.
Whisper transfer Providing a message or data to the recipient is generally referred to as a whisper transfer. A variety of user information is provided to the agent in order to facilitate personalized and quick customer interaction.
Transfer and run a self-service application In this scenario, a caller is transferred to a number and has a voice user interface presented to him to provide a personalized experience before an agent interacts with the caller. This scenario might be useful to limit user inputs before a call is transferred to an appropriate IVR application and/or an agent.
Multi-party conferencing CCXML is used to create conferencing applications that allow multiple users to talk to each other. These applications may also have a self-service component that requires dialog interaction provided by VoiceXML.

CCXML Benefits
As demonstrated in the variety of user scenarios enabled by CCXML, the standard is poised to make speech applications enterprise-ready and provide the much-needed impetus for customer adoption and growth of the voice Web. CCXML offers benefits to all stakeholders in the voice Web industry, including enterprises, application developers, service providers, and voice Web platform/ASP vendors.

CCXML enables developers of enhanced service platforms and ASP vendors to expand the capabilities of their service creation and service delivery environments and provide added value to their partners and customers.

Benefits To Enterprises
Enterprises benefit from CCXML in a number of ways. Standardization of call control capabilities enables enterprises to use multiple vendors to build a best-of-breed solution that meets their unique voice application needs. Companies have more flexibility and fewer risks than they would have with a single vendor strategy.

Additionally, deploying speech-enabled self-service applications in a contact center setting decreases the number of calls to operators, increases customer loyalty and improves the customer experience. Companies can expand their contact centers without having to hire more staff, and better manage their internal resources.

Enterprises can also make effective decisions on build versus buy strategies, as a variety of multiple application vendors will compete for the enterprise business with applications based on open standards.

Benefits To Service Providers
Wireline and wireless service providers can use the standards-based service creation and delivery functionalities available in voice Web application platforms to reduce operating costs associated with internal contact centers.

Voice Web platforms based on standards like CCXML also expand service providers' business opportunities in the voice application hosting market. Carriers can provide value-added voice application hosting services to enterprises that want the benefits of carrier-class call control and routing functionality and service creation capabilities. Enterprises also benefit because they maintain control of their corporate voice applications.

Benefits To Application Developers
Consulting companies and systems integrators can generate revenues by providing custom speech-enabled applications that deliver the benefits of CCXML. Developers only have to write an application one time, and then run it on all standards-compliant VoiceXML and CCXML interpreters. This helps developers sell their applications to a larger number of customers using different channels and with minimal changes, as standards-based interpreters are embedded in a variety of software platforms, gateways, and devices. Application developers can also differentiate themselves from incumbent service providers who deliver expensive, legacy applications that require significant capital expenditures to scale and operational expenditures to maintain appropriate levels of service.

CCXML also decreases development costs associated with labor and capital equipment by using free developer programs and programmers who are well versed in Web technologies and XML.

CCXML And VoiceXML: Complementary, Not Competing
CCXML is designed to work together with VoiceXML to fill in the gaps related to today's call control capabilities. While CCXML is interesting for standards enthusiasts and developers, enterprises are the real beneficiaries because they can finally look forward to deploying speech-enabled voice applications that benefit their customers.

CCXML is at draft stage, and it will be several months before the W3C adopts the specification. Still, the development of the specification and its future adoption represent an important milestone in the two-year journey of standards development for the voice application community.

Srinivas Penumaka is a product manager with Telera, a software company whose Voice Web Application Platform enables service providers to deliver a new class of advanced, business-centric voice applications to enterprise customers. For more information on standardization efforts, please visit www.w3.org/voice.

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