VoiceReview: Telera DeVXchange (Part I)

Review: Telera DeVXchange (Part I)

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Telera DeVXchange is a hosted VoiceXML developer community which allows
developers to develop and test VoiceXML-based applications using the combination
of a browser-based interface and a mobile phone. DeVXchange is primarily comprised of two components: AppBuilder & CodeCenter. AppBuilder is a desktop-based toolset which visually supports the development of dynamic applications based on server-side scripting technologies (Active Server Pages and/or Java Server Pages).

On the other hand, CodeCenter is a web-based VoiceXML platform which allows developers to register/test/debug VoiceXML applications using a combination of a web
browser and a regular phone. Similar to other hosted VoiceXML service providers such as Tellme and BeVocal, Voxeo CodeCenter’s focus is to provide VoiceXML developers with a hosted telephony environment which integrates a VoiceXML Interpreter, Speech Recognition, Text-to-Speech engine, speech verification etc.

VoiceXML Version Support

DeVXchange CodeCenter supports VoiceXML 2.0 including XML-based grammar
formats whereas DeVXchange AppBuilder still supports only VoiceXML 1.0 based
application code generation. Currently, the core of Telera Voice Web Application
Platform, including the tools that make up DeVXchange, is primarily based on top
of the Nuance Speech Recognition Platform. As a result, GSL grammars are supported.
Actually, CodeCenter also supports pre-complied and cached GSL grammars.

First looks – CodeCenter

An essential aspect of a hosted VoiceXML development platform is the ability to provide
developers with a basic tool to register/manage their VoiceXML applications.
CodeCenter enabled applications to be developed on external web servers and
allows the use of remote URL. Also provided is a Scratchpad-based
environment in which developers can quickly cut’n’paste and get started with
developing VoiceXML applications without the need of an external web server.

One useful aspect of CodeCenter is the quick validation function, called "Check Syntax,"
which performs a line-by-line syntax check of the root VoiceXML document
(the screenshot below shows the Check Syntax function in progress, pointing out a
spelling mistake of the tag ‘block’).

"Calling your Application"

After you have linked your remote VoiceXML application or have built a simple
scratchpad-based application, one of the various URLs (CodeCenter allows up-to
20 URLs) on the scratchpad can be activated as the current executing application. To test
the application, you can then dial 1-866-678-7788. For non-US developers, a
non-toll free number is also available (408) 626-4699. (Note: If you are still
using VoiceXML 1.0 based applications then the numbers are (866) 678-7798 and
(408) 626-4688.) A typical dialog such as would happen when calling your application would go something like the following:

  • Develeper dials (866) 678-7788.
  • CodeCenter: Welcome to DeVXchange CodeCenter. Please say or enter your
    CodeCenter Login Id.
  • Enters the 4 digit Login Id.
  • Please say or enter your PIN.
  • Enters the 4 digit PIN.
  • Your Call Number is 1001… continues to play the VoiceXML
    Application … Hello World from Hitesh.

Call Tracer

Detailed execution trace of the VoiceXML application is supported in
CodeCenter through a web-based tool called "Call Tracer." Resources,
grammars, recognition results, events, errors, attributes are highlighted in
different colors for easy viewing. The figure below shows Call Tracer in action.
Apart from the time when a call is in progress, the tracing information
encapsulated by Call Tracer is also available for later viewing.

Debug Logs

One of the features introduced by VoiceXML 2.0 was the <log> tag. This
tag allows developers of VoiceXML applications to uniformly log any required messages,
variable values etc. to either analyze them for future debugging needs or just for
an audit trail. This information is highlighted by the "Debug Logs" tool.
Similar to the Call Tracer tool, this information is also available after the call has
ended as well for future analysis.

Voice Recorder & Audio Converter

A rule of thumb in creating interactive dynamic speech recognition
applications is to use Text-to-Speech cautiously. VoiceXML allows the use of
pre-recorded audio as output prompts. To enable the rapid development of these
prompts, CodeCenter allows the developer to create these prompts in his/her own
voice (or maybe a voice of a colleague) using a phone. The Voice Recorder then
allows the developer to download the pre-recorded prompts into the web server.

Finally if you have already created a bunch of audio files in your computer
using your favorite audio recording tool, you can convert them into the audio
format supported by CodeCenter or your Text-to-Speech engine and telephony
boards using the Audio Converter. A number of formats are supported for inter-conversion,
including Windows WAV, Dialogic VOX, Sun Microsystems AU and Macintosh HCOM.


The "tech resources" section of the CodeCenter community provides a
bunch of technical resources which can be useful for beginning to advanced
developers. This includes code and VoiceXML application samples (including
dynamic samples using ASP/JSP scripting technology), a VoiceXML Reference Guide, a
set of professionally recorded reusable audio-prompts and technical white-papers.

To be Continued

In the next issue of our continuation of the review of Telera DeVXchange 
we will take a look at the Grammar Verifier tool, outbound calling functionality and we will also review some interesting extensions that Telera has developed for call-control within VoiceXML applications.


About Hitesh Seth

A freelance author and known speaker, Hitesh is a
columnist on VoiceXML technology in XML Journal and regularly writes for other
technology publications including Java Developer’s Journal, Web Services
Journal and The Computer Bulletin on emerging technology topics such as J2EE, Microsoft .NET, XML, Wireless
Computing, Speech Applications, Web Services & Enterprise/B2B Integration. He is the
conference chair for VoiceXML
Planet Conference & Expo
. Hitesh received his
Bachelors Degree from the Indian Institute of Technology Kanpur (IITK), India.
Feel free to email any comments or suggestions about the articles featured in
this column at hks@hiteshseth.com.

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