Larson Technical Services: Voice Technology Consulting

Exercise 7.3

VoiceXML has build-in grammars for Boolean, date, digits, currency, number, phone, and time. However, the definition of these grammars has not been standardized.

A. Retrieve definition for one of the build-in grammars from at least two different VoiceXML venders. Compare the two grammars and identify any differences.

Most venders do not specify the definition of built-in grammars. After using the following program to test the words accepted by a field with type Boolean


<?xml version="1.0"?>
<vxml version="2.0">  

<!-- evaluate use of "boolean"  -->

<form id = "data_collection">

<field name="test" type = "boolean">
     <prompt>answer? </prompt>
</field>

<block>
     <prompt> answer is  <value expr="test"/>
     </prompt>
</block>
</form>
</vxml>  

The BeVocal engine accepts "true" but not "sure."

The TellMe engine accepts "sure," but not" true."

B. If an application is to be ported across multiple VoiceXML interpreters, do you recommend using default grammars? Why?

No. Avoid using built in grammars because the resulting applications may not respond in the same way if they are ported to another engine. Replace build-in grammars by specified grammars to ensure portability.

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