Introduction to VXML

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Introduction to VXML
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What is VXML?

• Voice Extensible Markup Language
• Used in
• telephone-based speech applications
• voice browsing of the web

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How does VXML work?

• Two main components
• tags -- control what the program does
• grammars -- control what speech is recognized
  what the user can say

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Basic VXML tags

• ltvxmlgt -- defines a VXML application
• ltformgt -- basic component of a dialog
• ltpromptgt -- says something to the user
• ltfieldgt -- holds information supplied by user
• ltgrammargt -- defines what user can say
• ltfilledgt -- what to do once user says something

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VXML Hierarchy

• ltvxmlgt contains one or more ltformgt
• ltformgt may contain one or more ltpromptgt and does
  contain one or more ltfieldgt
• ltfieldgt contains one or more ltpromptgt but one and
  only one ltgrammargt and an optional ltfilledgt

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Example 1
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Tonys Tips 1

• All files must end with the extension .vxml
• Use a simple editor such as Notepad or the editor
  provided by BeVocal. Do not use Word -- it tends
  to add extra hidden formatting
• All tags occur in pairs (e.g., ltformgt and
  lt/formgt)
• When using ltpromptgt avoid punctuation and
  capitalization

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VXML Grammars

• Two types of grammars
• Programmer specified -- you decide what can be
  said
• Built-in or pre-defined
• Two tags related to grammars
• ltgrammargt -- what can be said
• ltfilledgt -- what to do once you recognize
  something

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Built-in Grammars
OK
OK
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Example 2a
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Example 2b
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Recognizing phrases

• Single words
• news sports weather exit
• phrases
• (i want the news)
• Combined
• ((i want the) news sports)
• ((i want the) news sports (home section))
• Saying something optional
• (?(i want the) news sports ?please)

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Using slots

• Problem ltfieldgt holds entire phrase that is
  recognized
• would have to write a separate rule for each
  possible phrase (i.e., the vocabulary problem)
• Slots are a useful shortcut when recognizing
  phrases
• ((i want the) news sports (home section))
• ((i want the)
• news ltsection newsgt
• sports ltsection sportsgt
• (home section) ltsection home gt )

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Example 2c
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More on grammars

• Grammars do not have to be defined directly in
  vxml file
• can be defined in a separate file with .gsl
  extension (see example 3)

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Tonys Tips 2

• avoid capitalizing words or using punctuation
  when defining a grammar
• Use built-in grammars whenever possible
• Use slots when trying to recognize phrases
• Use a separate grammar file if certain things
  will be recognized repeatedly (e.g. example 3)

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So far...

• The metaphor is VXML as a form
• Dialog is overdetermined (i.e., the system is in
  control)

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What about...
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Design considerations
Main menu
people menu
Undergrad menu
Grad menu
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Design considerations
Main menu
people menu
Undergrad menu
Grad menu
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Design considerations
Main menu
people menu
Undergrad menu
Grad menu
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Example 3
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Example 4
Main menu
grammar
ex4_psych.vxml
psychology.gsl
ex4_undergr.vxml
ex4_grad.vxml
ex4_people.vxml
people menu
Undergrad menu
Grad menu
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Tonys Tips 3

• When using external grammars the rule name must
  start with a capital letter and is case sensitive
  (e.g., Fish is different from FISH)
• Plan first, then write code
• Break the project into pieces
• Test each small piece individually then combine

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Adding flexibility

• Handling speech recognition errors
• Handling long periods of silence
• Help
• Repeating
• Exiting/Hanging up gracefully

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Adding flexibility

• Given/new information (e.g., emphasis)
• This implementation of VXML does not allow you to
  change emphasis despite having tags ltemphasisgt
  and ltprosodygt

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You can get this correct
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Additional options

• Change the timeout length
• Say as feature
• Ex. system can say a series of numbers in
  telephone style
• Use pre-recorded sounds (i.e., .wav files)
• Change the voice

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Tonys Tips 4

• Start early
• Reuse code -- dont reinvent the wheel
• Put comments in your code
• If you get stuck ask someone for help
• See Tonys Tips 1-3

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FUll flow chart Example 3/4