SDLC

Introduction

The Web has revolutionized how people communicate and share information.
Businesses deploy millions of web services to consumers with Internet access.
Internet and telephony used to be two separate technologies requiring a
specialized telecom expert to build applications accessible over the phone.
VoiceXML bridges the gap; it leverages the existing web infrastructure and
enables web developers to build voice-enabled web applications accessible from
any telephone, by anyone, anywhere, anytime.

Users interact with VoiceXML applications via a Voice User Interface (VUI)
similar to the way they interact with traditional web applications via a
Graphical User Interface (GUI). Poorly designed VUI frustrate users quickly,
resulting in operator assistance or disconnected calls. It does not matter how
powerful the application is or how many features it supports, if users cannot or
will not use it. Therefore, a well-designed VUI is essential to the success of
any voice application.

VoiceXML is designed for the rapid development of voice web applications, but
it does not address usability. A quality VoiceXML application requires a
well-designed VUI. This paper discusses the VoiceXML application development
lifecycle focusing on application usability. The paper also describes key roles
and skills required in each phase of the development cycle. It looks at how the
HP VoiceXML tools help developers simplify the development process and improve
the usability of their VoiceXML applications before deploying to the

HP OCMP VoiceXML platform.

This paper targets Java/J2EE developers who want to put a voice interface on
their existing web applications or develop new voice applications leveraging
their web skills. For VoiceXML background information, please see

Developing voice-enabled web services. (Log-in required)

VoiceXML application challenges

VoiceXML applications require humans to converse with a computer. Designing a
usable VUI is more difficult than designing a GUI. Challenges include:

• VUI is invisible. Information is transient; callers forget what they just
  heard.
  
  
  
   


• Conversation is linear. Callers get very impatient listening to long
  prompts or hearing messages played repeatedly.
  
  
  
   


• Caller is "lost in space." Callers get disoriented when they get
  distracted or when there are many layers of spoken menus.
  
  
  
   


• Caller can say anything. Humans make mistakes. The big challenge is to cue
  the caller with clear wording so that the expected responses are received.

Callers hang up when they get confused, become impatient with long prompts,
or think the application is not working.

Speech recognition is another VUI challenge. Speech recognition technologies
have advanced dramatically, but speech recognition is still not perfect.
Background noise and poor voice quality from poor telephone connections or
low-quality microphones may cause the speech engine to misinterpret the caller
inputs, leading the application to perform incorrect actions.

VoiceXML application development life cycle

The VoiceXML application development life cycle is similar to that of a web
application but includes VUI design and speech recognition tuning. The
development cycle consists of six phases:

1. Definition


2. Design


3. Development


4. Testing


5. Pilot/Tuning


6. Deployment/Monitoring

VUI design and usability testing are critical for developing a successful
VoiceXML application. Iterative usability tuning is required throughout the
development cycle to build useful VoiceXML applications.

Key roles and responsibilities

Although VoiceXML is easy to learn, building a successful VoiceXML application
requires not only software development skills, but other skills like
understanding human factors for the telephone interface, linguistics, speech
recognition and audio production.



 

Role	Responsibility
Business managers	Includes marketing manager and project manager. Responsible for defining business requirements, allocating resources and budget, and managing the project to completion.
Application architect	Design the application.
VUI designer	Understand speech sciences and linguistics; design, test, and refine dialogs and grammars.
Speech scientist & phonetician	Understands computational linguistics and phonetics, tunes the ASR engine, maintains phonetic dictionaries.
Usability test engineer	Verifies and analyzes dialogs, understands how well the application actually works for the intended callers
Audio production team	Includes the voice talent, creative director, and recording engineers. Responsible for producing audio prompts
Software developer	Implements, integrates and tests front-end VoiceXML and backend code using various technologies such as XML, JSP, and J2EE
System administrator	Deploys and monitors the behaviors of the VoiceXML application.

Definition phase

During the definition phase, the business managers and application architect
collaborate to address the following key issues:

• What is the purpose of developing the application (e.g. provide new
  service, solve customer problem, reduce operational cost, etc.)?


• What is the business case?


• What is the callers' profile (age, gender, general background such as
  immigrant, education level, etc.)? What is their usage profile? How will they
  use the application and what are their expectations?


• What are the use cases, features, and required functionality?


• What is the project scope?


• What are the performance, capacity, and reliability requirements?


• What platform, VoiceXML browser, hosting portal, speech recognition and
  Text To Speech (TTS) engine, and document server are they going to use? What
  back-end systems (business logic) will the application integrate?

In addition, the VUI requirements have to be clearly defined based on the
caller's profile, the usage and the expected caller's experience:

• What is the persona for the application (gender, age, personality)?


• How should the application be perceived (serious, casual, humorous)?


• What are the spoken languages in the deployment region?


• What are the typical environments (e.g. in an airport, car, quiet office)
  in which the application will be used?


• How does the application work in a real world situation and what are the
  user scenarios?

Design phase

The design phase can be broken into two stages: prototype and detailed design.

Prototype

The application architect and the VUI designers decide on the application
dialog style (i.e., directed dialog¹,
mixed initiative²,
natural language³
dialog) and create a prototype of the application. The prototype describes
user scenarios, the initial high-level call flow, prompts, and grammars. It is
important to start the usability analysis during this phase. A technique
called "Wizard of Oz testing" involves using a human to play the role of the
computer. This person reads the application prompts and processes the caller's
inputs to test the dialogs and the call flow before coding starts.

 

---

¹ The application prompts the caller by asking a question
and then waits for the caller to respond.

² Both application and the caller initiate and direct the
conversation.

³ "Natural" human-like interaction between the application
and the caller.

 

Detailed design

The application architect and the VUI designers make detailed design decisions
based on the requirements specification and the prototype. The detailed design
includes:

• The application architecture, required components, types of
  implementation, and the back-end systems that will be integrated. The
  application is composed of the voice front-end (VoiceXML page) and back-end
  server components. The architect needs to consider performance when
  determining front-end functionality. This helps the application avoid
  unnecessary remote HTTP requests to the back-end server, which create
  conversation delays.
  
  
  
   


• The call flows and detailed elements associated with each dialog state:
  actions, error handling, prompt and grammar definitions, input mode [voice,
  DTMF (touch tone) or both], universal commands, help, synthesized speech,
  recorded audio, and the interfaces for accessing the back-end logic and
  databases.

A good VUI design must consider:

• Prompt: Prompt should be simple and clear to intuitively lead the caller
  to an expected (anticipated) outcome.
  
  
  
   


• Memory load: Studies show that, under normal circumstances, callers have a
  short-term memory of approximately six words. Ideally, the number of choices
  for callers to select should be four or less. Otherwise, callers become
  confused and forget the choices presented to them.
  
  
  
   


• Service reachability: It is not pleasant for a caller to go through a
  large number of steps before he reaches a service. Callers start to get
  impatient with more than five steps. Minimize the number of steps a caller
  must take to reduce frustration.
  
  
  
   


• Navigation: Provide a way to navigate back and forth between various
  dialog steps. The caller should be able to go to different parts of the dialog
  easily.
  
  
  
   


• Phonetic similarity: Provide a clear set of choices for caller to select.
  Avoid choices with similar pronunciations.
  
  
  
   


• Grammar collision: Don't give the same choices at different locations in
  the conversation. If the same grammar element appears in more than one context
  but has a different function, callers become confused.
  
  
  
   


• Help: Callers need help messages to explain things that they do not
  understand.
  
  
  
   


• Error handling: Humans make mistakes. Graceful error handling decreases
  dependency on operators.
  
  
  
   


• Confirmation: Confirm the caller's response to ensure that the machine got
  exactly what the caller said and not a different selection. This gives the
  caller a feeling of confidence.
  
  
  
   


• User update: Let the user know what is going on and keep him engaged.
  Back-end service actions may be slow.
  
  
  
   


• Timeouts: Specify reasonable timeout values to mange the flow of the
  dialog and keep the user engaged.
  
  
  
   


• Educate ahead: Train callers on how to use the application and what they
  can expect. For example, provide a tutorial option for the first-time caller.
  This tutorial might play sample dialogs describing how to interact with to the
  application. Another option is to send a caller a web page link with dialog
  samples when they sign up for a voice service.

Tooling

These tools are useful during the design phase:

1. 
   
   SUEDE is a speech interface prototype tool developed at UC-Berkeley. SUEDE
   offers an electronic version of the Wizard of Oz technique that captures test
   data, allowing designers to analyze the VUI.
   
   
   
    


2. Microsoft® Office Visio, with drag-and-drop symbols, helps with designing
   high-level call flow.

Development phase

The development phase involves grammar development, audio production, software
development, and back-end integration. The VUI designer, audio production team
and software developer work on different components of the application.

Grammar development

The grammar definition is a key part of the VUI and is tightly entwined with
the dialog style and prompts. While creating the grammars, the dialog
designers must collaborate very closely with the software developers and audio
production team to iteratively test and refine the prompt wording and
grammars. Well-tuned grammars can reduce many types of recognition errors.

Audio production

The audio production team records the prompts and creates the audio files. The
VUI designers often work with the voice talent to create the application
persona, such as age (young or mature), personality (calm, peppy, romantic,
trustworthy or authoritative), socioeconomic status, education level and etc.

Software development

Based on the detailed call flow design, the software development team
implements the VoiceXML application. They:

• Create the VoiceXML project and structure


• Develop code for complete call flow, such as output prompts (TTS and
  audio)


• Handle errors, help, and universal navigation commands


• Integrate with the back-end using JSP, servlets, CGI, and PHP

In addition, the team is also responsible for developing the server-side
logic and integrating with other existing applications or databases. In general,
the software development team consists of several sub-teams responsible for the
front-end components, the back-end logic, and system integration.

Usability analysis and VUI refinement is very important during this phase to
ensure that the implementation closely follows the call flow and detailed
design.

Tooling



 

HP OpenCall provides

VoiceXML development tools for Eclipse. This tool accelerates the
development of VoiceXML applications that run on the HP OCMP VoiceXML
platform. In addition to assisting the developer in creating, editing, and
validating static and dynamic JSP VoiceXML and grammar documents, the tools
provide Dialog Analysis capability to help detect usability issues. The Dialog
Analysis displays potential usability problems related to memory load, service
reachability, grammar collision and phonetic similarity. The tool also
displays statistics, broken links, warnings, and a metric summary of the
VoiceXML document.

 

Testing phase

All components should undergo independent unit testing. After the individual
components have passed unit testing, the application logic, expected
functionality, and dialog flow are tested. Testing can be performed in a
simulated environment with Text to Speech (TTS) and Automatic Speech
Recognition (ASR) support so developers can actually "dial up" the
application.

Usability testing is required for all dialogs, actions, navigation, and help
prompts associated with each dialog. The caller's response patterns can indicate
the trouble spots, for example, using words like "uh," and "umm," and pausing
for a long time after a prompt. The usability engineers evaluate the human
interaction experience, identify ambiguous and inconsistent direction, make sure
services can be reached in a reasonable number of steps, and look for missing
universal commands. The usability engineer's primary objective is to make sure
the application provides the required service.

Tooling

The HP OpenCall development tools tightly integrate with HP OCMP VoiceXML
simulated test environment, HP OCMP VoiceXML SDK. Developers deploy the
application to the simulated test environment, and dial up the VoiceXML
application using a simulated soft phone. The HP OCMP VoiceXML SDK allows
developers to use the logging technique <log> to log to Call Data Record (CDR)
and test the application logic, the conversation flow, and the speech
recognition. The event logs and CDR capture user-computer interaction and call
control events, and contain detailed information for each call to the
application. This includes HTTP requests, fetched documents, VoiceXML events,
properties (i.e., timeout, bargein, fetchtimeout), and waveform recognition
results.

 

Pilot/tuning phase

In this phase, the application runs on a real telephony network with a sample
group of live callers. The goal is to capture real data, analyze application
behavior, identify and tune problems in the grammars and speech recognition
before the final deployment. Tuning may require only minor changes to prompts
or grammars, or a modification or addition to the recognizer's phonetic data,
but it can be repetitive.

Dialog tuning

Analyzing log file data helps to understand the application's behavior:

• What are the task completion and dropout rates?


• Which state of the dialog flow causes the most dropouts?

Post-test interviews are a good way to capture usability feedback:

• Why did a caller abandon certain tasks or not use a specific feature such
  as universal commands, barge-in, or help?


• Were the prompts confusing?


• Did the caller think some options were unnecessary?

Refine the prompts, grammars, parameters, and other dialog elements, and test
again!

Speech recognition tuning

Tune speech recognition accuracy and grammar, including:

• ASR parameters


• Acoustics models


• Confidence thresholds


• Phonetic dictionary (adding alternate pronunciations)

Successful tuning requires extensive knowledge speech recognition techniques
and of the speech recognition engine being used. Speech scientists should be
involved in the speech recognition tuning.

Performance and load testing

Performance and load testing ensure that the system can handle the expected
call volume within the expected response time.

Tooling

The HP OCMP VoiceXML SDK and Dialog Verification tool allow developers and
usability engineers to perform detailed analysis of the application behavior.
This helps developers locate trouble spots for recognition errors. Once
trouble spots are identified, the application can be "tuned."

Deploy/monitoring phase

The final stage is to deploy the application. System administrators need to
continuously monitor logged calls and reports, periodically tune and enhance
the application to adapt to changing caller profiles and usages.

Tooling

The HP VoiceXML development tools provide the ability to package and publish
the VoiceXML application to the document server. HP OCMP VoiceXML SDK provides
event logging, online reporting, and CDR to continuously monitor the
application.

Summary

The most important element of a voice application is the VUI usability.
Callers abandon applications quickly in response to a poor VUI. Usability must
be addressed in all stages of the development lifecycle. In particular,
callers' involvement, iterative testing, and VUI tuning are critical when
building quality VoiceXML applications.

Using development and testing tools reduces both the complexity and time
required to develop a VoiceXML application with a good VUI.

The HP OCMP vXML Developer Toolkit provides integrated Java and VoiceXML
development environments and helps developers implement the front-end VoiceXML
VUI and the back-end service components. The tools are specifically designed to
address the common VUI issues, allowing developers to iteratively analyze and
catch usability problems at development time. The OCMP VoiceXML SDK and the
Dialog Verification tool help in the testing and tuning of the call flow,
dialogs, and speech recognition problems.

HP OpenCall provides developers with development tools and testing
environment, which help improve the application usability, simplify the
development process and reduce the development time for building VoiceXML
applications that run on the HP OCMP VoiceXML platform.

For more information



 

Books

• Voice user interface design by Michael H. Choen, James P.
  Giangola, Jennifer Balogh; Addison-Wesley Professional. February 2004.


• VoiceXML—an introduction to developing speech applications, first
  edition by James A. Larson; Prentice Hall. June 2002.


• Voice-enabling applications: VoiceXML and beyond by Kenneth
  R. Abbott; APress. November 2001.


• VoiceXML: Professional developer's guide by Chetan Sharma and
  Jeff Kunins; Wiley Publishers. December 2001.


• Voice application development with VoiceXML, first edition by
  Rick Beasley, Kenneth Michael Farley, John O'Reilly, Leon Squire, Kenneth
  Farley; Sams Publishing. August 2001.