vxml:需要在线语法方面的帮助

我正在查看VXML.org中的一些VXML脚本示例。当我调用脚本时,提示将播放,但它根本不会接收任何输入。当我说话时,它回答“没有输入”。我是否可能缺少一些指示用户输入的标记?这是网站上的示例脚本:

<?xml version="1.0" encoding="UTF-8"?>
<vxml version = "2.1">
   <link next="#MainMenu">
      <grammar type="text/gsl">[main back begin]</grammar>
   </link>

   <form id="MainMenu">
      <block>
         <prompt bargein="false">
            This is the Hello World Main Menu.
         </prompt>
      </block>

      <field name="MeatOrPlant">
         <prompt>
            Are you a "Carnivore" or "Vegetarian".
         </prompt>

         <grammar type="text/gsl">
            <![CDATA[[
              [vegetarian plant veggie] {<MeatOrPlant "plant">}
              [meat carnivore flesh animal] {<MeatOrPlant "meat">}
            ]]]>
         </grammar>

         <noinput>
            <prompt>
               I did not hear anything. Please try again.
            </prompt>
            <reprompt/>
         </noinput>

         <nomatch>
            <prompt>
               I did not recognize that lifestyle choice.  Please try again.
            </prompt>
            <reprompt/>
         </nomatch>

      </field>
      <filled>
         <if cond="MeatOrPlant == 'meat'">
            <goto next="#Meat"/>
            <elseif cond="MeatOrPlant == 'plant'"/>
            <goto next="#Plant"/>
         </if>
      </filled>
   </form>

   <form id="Meat">
      <field name="BackToMain">
         <prompt>
            PETA is coming for you, be afraid.
            If you wish to try again, please say Main.
         </prompt>
      </field>
      <filled>
         <!-- no way this will get hit -->
      </filled>
   </form>

   <form id="Plant">
      <field name="BackToMain">
         <prompt>
            Protein is the spawn of the devil.
            If you wish to try again, please say "Main".
         </prompt>
      </field>
      <filled>
         <!-- no way this will get hit -->
      </filled>
   </form>
</vxml>

有人知道吗?蒂亚