Voice Extensible Markup Language (VoiceXML) 2.1

1 Introduction

The popularity of VoiceXML 2.0 [VXML2] spurred the development of numerous voice browser implementations early in the specification process. [VXML2] has been phenomenally successful in enabling the rapid deployment of voice applications that handle millions of phone calls every day. This success has led to the development of additional, innovative features that help developers build even more powerful voice-activated services. While it was too late to incorporate these additional features into [VXML2], the purpose of VoiceXML 2.1 is to formally specify the most common features to ensure their portability between platforms and at the same time maintain complete backwards-compatibility with [VXML2].

This document defines a set of 8 commonly implemented additional features to VoiceXML 2.0 [VXML2].

2 Referencing Grammars Dynamically

As described in section 3.1 of [VXML2], the <grammar> element allows the specification of a speech recognition or DTMF grammar. VoiceXML 2.1 extends the <grammar> element to support the following additional attribute:

Exactly one of "src", "srcexpr", or an inline grammar must be specified; otherwise, an error.badfetch event is thrown.

The following example demonstrates capturing a street address. The first field requests a country, the second field requests a city, and the third field requests a street. The grammar for the second field is selected dynamically using the result of the country field. The grammar for the third field is selected dynamically using the result of the city field.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml" 
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">

  <form id="get_address">
    <field name="country">
      <grammar type="application/srgs+xml" src="country.grxml"/>
      <prompt>Say a country.</prompt>
    </field>

    <field name="city">
      <grammar type="application/srgs+xml" srcexpr="country + '/cities.grxml'"/>
      <prompt>What city in <value expr="country"/>.</prompt>
    </field>

    <field name="street">
      <grammar type="application/srgs+xml" srcexpr="country + '/' + city + '/streets.grxml'"/>
      <prompt> What street in <value expr="city"/> are you looking for? </prompt>
    </field>

    <filled>
      <prompt> 
       You chose 
       <value expr="street"/> 
       in 
       <value expr="city"/> 
       <value expr="country"/>
      </prompt>
      <exit/>
    </filled>
  </form>
</vxml>

3 Referencing Scripts Dynamically

As described in section 5.3.12 of [VXML2], the <script> element allows the specification of a block of ECMAScript [ECMA] client-side scripting language code, and is analogous to the [HTML4] <SCRIPT> element. VoiceXML 2.1 extends the <script> element to support the following additional attribute:

Exactly one of "src", "srcexpr", or an inline script must be specified; otherwise, an error.badfetch event is thrown.

The following example retrieves a script from a URI that is composed at run-time using the variable scripts_baseuri.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml" 
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">

  <var name="scripts_baseuri" expr="'http://www.example.org/'"/>

  <form>
    <script srcexpr="scripts_baseuri + 'lib/util.js'"/>
  </form>
</vxml>

4 Using <mark> to Detect Barge-in During Prompt Playback

As described in section 3.3.2 of [SSML], the <mark> element places a marker into the text/tag sequence. An SSML processor must either allow the VoiceXML interpreter to retrieve or must inform the interpreter when a <mark> is executed during audio output.

[SSML] defines a single attribute, "name", on the <mark> element, allowing the programmer to name the mark. VoiceXML 2.1 extends the <mark> element to support the following additional attribute:

Exactly one of "name" and "nameexpr" must be specified; otherwise, an error.badfetch event is thrown.

As described in section 4.1.1 of [VXML2], the <mark> element is permitted in conforming VoiceXML documents, but [VXML2] does not specify a standard way for VoiceXML processors to access <mark> element information. Processors of conforming VoiceXML 2.1 documents must set the following two properties on the application.lastresult$ object whenever the application.lastresult$ object is assigned (e.g. a <link> is matched) and a <mark> has been executed.

When these properties are set on the application.lastresult$ object, if an input item (as defined in section 2.3 of [VXML2]) has also been filled and has its shadow variables assigned, the interpreter must also assign markname and marktime shadow variables, the values of which equal the corresponding properties of the application.lastresult$ object.

When a <mark> is executed during the flushing of the prompt queue as a result of encountering a fetchaudio, the application.lastresult$ object should not be modified and no shadow variables should be assigned.

The following example establishes marks at the beginning and at the end of an advertisement. In the <filled>, the code checks which mark, if any, was last executed when bargein occurred. If the "ad_start" mark is executed but "ad_end" is not, the code checks that at least 5 seconds of the advertisement has been played and sets the played_ad variable appropriately.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml" 
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">

  <var name="played_ad" expr="false"/>

  <form>   
    <field name="team">
      <prompt>
        <mark name="ad_start"/>
        Baseball scores brought to you by Elephant Peanuts.
        There's nothing like the taste of fresh roasted peanuts.
        Elephant Peanuts. Ask for them by name.
        <mark name="ad_end"/>
        <break time="500ms"/>
        Say the name of a team. For example, say Boston Red Sox.
      </prompt>
  
      <grammar type="application/srgs+xml" src="teams.grxml"/>
  
      <filled>
        <if cond="typeof(team$.markname) == 'string' &amp;&amp;
           (team$.markname=='ad_end' || 
           (team$.markname=='ad_start' &amp;&amp;
              team$.marktime &gt;= 5000))">
          <assign name="played_ad" expr="true"/>
        <else/>
          <assign name="played_ad" expr="false"/>
        </if>
      </filled>
  
    </field>
  </form>   

</vxml>

5 Using <data> to Fetch XML Without Requiring a Dialog Transition

The <data> element allows a VoiceXML application to fetch arbitrary XML data from a document server without transitioning to a new VoiceXML document. The XML data fetched by the <data> element is bound to ECMAScript through the named variable that exposes a read-only subset of the W3C Document Object Model [DOM].

Attributes of <data> are:

Exactly one of "src" or "srcexpr" must be specified; otherwise, an error.badfetch event is thrown. If the content cannot be retrieved, the interpreter throws an error as specified for fetch failures in Section 5.2.6 of [VXML2].

Platforms should support parsing XML data into a DOM. If an implementation does not support DOM, the name attribute must not be set, and any retrieved content must be ignored by the interpreter. If the name attribute is present, these implementations will throw error.unsupported.data.name.

If the name attribute is present, and the returned document is XML as identified by [RFC3023], the VoiceXML interpreter must expose the retrieved content via a read-only subset of the DOM as specified in Appendix D. An interpreter may support additional data formats by recognizing additional media types. If an interpreter receives a document in a data format that it does not understand, or the data is not well-formed as defined by the specification of that format, the interpreter throws error.badfetch. If the media type of the retrieved content is one of those defined in [RFC3023] but the content is not well-formed XML, the interpreter throws error.badfetch.

Like the <var> element, the <data> element can occur in executable content or as a child of <form> or <vxml>. In addition, it shares the same scoping rules as the <var> element. If a <data> element has the same name as a variable already declared in the same scope, the variable is assigned a reference to the DOM exposed by the <data> element.

If use of the DOM causes a DOMException to be thrown, but the DOMException is not caught by an ECMAScript exception handler, the VoiceXML interpreter throws error.semantic.

Like the <submit> element, when an ECMAScript variable is submitted to the server its value is first converted into a string before being submitted. If the variable is an ECMAScript Object the mechanism by which it is submitted is not currently defined. If a <data> element's namelist contains a variable which references recorded audio but does not contain an enctype of multipart/form-data [RFC2388], the behavior is not specified. It is probably inappropriate to attempt to URL-encode large quantities of data.

If the value of the src or srcexpr attribute includes a fragment identifier, the processing of that fragment identifier is platform-specific.

In the examples that follow, the XML document fetched by the <data> element is in the following format:

<?xml version="1.0" encoding="UTF-8"?>
<quote xmlns="http://www.example.org">
  <ticker>F</ticker>
  <name>Ford Motor Company</name>
  <change>1.00</change>
  <last>30.00</last>
</quote>

The following example assigns the value of the "last" element to the ECMAScript variable "price":

<data name="quote" src="quote.xml"/> 
<script><![CDATA[
  var price = quote.documentElement.getElementsByTagNameNS("http://www.example.org", "last").item(0).firstChild.data;
]]></script>

The data is fetched when the <data> element is executed according to the caching rules established in Section 6.1 of [VXML2].

Before exposing the data in an XML document referenced by the <data> element via the DOM, the interpreter should check that the referring document is allowed to access the data. If access is denied the interpreter must throw error.noauthorization.

The following example retrieves a stock quote in one dialog, caches the DOM in a variable at document scope, and uses the DOM to playback the quote in another dialog.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml" 
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">
  <var name="quote"/>
  <var name="ticker" expr="'f'"/>

  <form id="get_quote">
     <block>
        <data name="quote" srcexpr="'http://www.example.org/getquote?ticker=' + ticker"/>
        <assign name="document.quote" expr="quote.documentElement"/>
        <goto next="#play_quote"/>         
     </block>
  </form>

  <form id="play_quote">

     <script><![CDATA[
     // retrieve the value contained in the node t from the DOM exposed by d
     function GetData(d, ns, t, nodata)
     {
        try {
           return d.getElementsByTagNameNS(ns, t).item(0).firstChild.data;
        }
        catch(e)
        {
           // the value could not be retrieved, so return this instead
           return nodata;
        }
     }
     ]]></script>

     <block>
        <!-- retrieve the change in the stock's value -->
        <var name="change" expr="GetData(quote, 'http://www.example.org', 'change', 0)"/>
        <var name="last" expr="GetData(quote, 'http://www.example.org', 'last', 0)"/>
        <var name="last_parts" expr="last.split('.')"/>

        <!--play the company name -->
        <audio expr="ticker + '.wav'"><value expr="GetData(quote, 'http://www.example.org', 'name', 'unknown')"/></audio>
        <!-- play 'unchanged, 'up', or 'down' based on zero, positive, or negative change -->
        <if cond="change == 0">
           <audio src="unchanged_at.wav"/>
        <else/>
           <if cond="change &gt; 0">
              <audio src="up.wav"/>
           <else/> <!-- negative -->
              <audio src="down.wav"/>
           </if>
           <audio src="by.wav"/>
           <!-- play change in value as positive number -->
           <audio expr="Math.abs(change) + '.wav'"><value expr="Math.abs(change)"/></audio>
           <audio src="to.wav"/>
        </if>
        <!-- play the current price per share -->
        <audio expr="last_parts[0] + '.wav'"><value expr="last_parts[0]"/></audio>
        <if cond="Number(last_parts[1]) &gt; 0">
           <audio src="point.wav"/>
           <audio expr="last_parts[1] + '.wav'"><value expr="last_parts[1]"/></audio>
        </if>
     </block>
  </form>
</vxml>

6 Using <foreach> to Concatenate Prompts and Loop through Executable Content

The <foreach> element allows a VoiceXML application to iterate through an ECMAScript array and to execute the content contained within the <foreach> element for each item in the array. The <foreach> element may appear within executable content and within <prompt> elements. Within executable content, except within a <prompt>, the <foreach> element may contain any elements of executable content; this introduces basic looping functionality by which executable content may be repeated for each element of an array. When <foreach> appears within a <prompt> element, it may contain only those elements valid within <enumerate> (i.e. the same elements allowed within <prompt> less <meta>, <metadata>, and <lexicon>); this allows for sophisticated concatenation of prompts as illustrated in this section.

Attributes of <foreach> are:

Both "array" and "item" must be specified; otherwise, an error.badfetch event is thrown.

The iteration process starts from an index of 0 and increments by one to an index of array_name.length - 1, where array_name is the name of the shallow copied array operated on by the <foreach> element. For each index, a shallow copy or reference to the corresponding array element is assigned to the item variable (i.e. <foreach> assignment is equivalent to item = array_name[index] in ECMAScript); the assigned value could be undefined for a sparse array. VoiceXML 2.1 does not provide break functionality to interrupt a <foreach>.

The following example calls a user-defined function GetMovieList that returns an ECMAScript array. The array is assigned to the variable named 'prompts'. Upon entering the <field>, if a noinput or a nomatch event occurs, the VoiceXML interpreter reprompts the user by executing the second <prompt>. The second <prompt> executes the <foreach> element by iterating through the ECMAScript array 'prompts' and assigning each array element to the variable 'thePrompt'. Upon each iteration of the <foreach>, the interpreter executes the contained <audio> and <break> elements.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml"
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">

  <script src="movies.js"/>

  <form id="pick_movie">
  
    <!-- 
    GetMovieList returns an array of objects
      with properties audio and tts.
      The size of the array is undetermined until runtime.
    -->  
    <var name="prompts" expr="GetMovieList()"/>

    <field name="movie">
      <grammar type="application/srgs+xml" src="movie_names.grxml"/>
  
      <prompt>Say the name of the movie you want.</prompt>
  
      <prompt count="2">
        <audio src="prelist.wav">When you hear the name of the movie you want, just say it.</audio>
        <foreach item="thePrompt" array="prompts">
          <audio expr="thePrompt.audio"><value expr="thePrompt.tts"/></audio>
          <break time="300ms"/>
        </foreach>
      </prompt>
  
      <noinput>
        I'm sorry. I didn't hear you.
        <reprompt/>
      </noinput>
  
      <nomatch>
        I'm sorry. I didn't get that.
        <reprompt/>
      </nomatch>
  
    </field>
  </form>
</vxml>

The following is a contrived implementation of the user-defined GetMovieList function:

function GetMovieList()
{
  var movies = new Array(3);
  movies[0] = new Object();
  movies[0].audio = "godfather.wav"; movies[0].tts = "the godfather";
  movies[1] = new Object();
  movies[1].audio = "high_fidelity.wav"; movies[1].tts = "high fidelity";
  movies[2] = new Object();
  movies[2].audio = "raiders.wav"; movies[2].tts = "raiders of the lost ark";
  
  return movies;
}

When the interpreter queues the second <prompt>, it expands the <foreach> element in the previous example to the following:

<audio src="godfather.wav">the godfather</audio>
<break time="300ms"/>
<audio src="high_fidelity.wav">high fidelity</audio>
<break time="300ms"/>
<audio src="raiders.wav">raiders of the lost ark</audio>
<break time="300ms"/>

The following example combines the use of the <mark> and <foreach> elements to more precisely identify which item in a list of movies the user has selected. During each iteration of the <foreach>, the interpreter stores the current item in the array to the variable movie. Upon execution of the <mark> element, the name of the <mark> is set to the current value of the variable movie_idx which is incremented during each iteration of the loop.

In the <filled>, if the form item variable mov is set to the value "more", indicating the user's desire to hear more detail about the movie name that was played when the user barged in, the code retrieves the index of the desired movie in the movies array from mov$.markname. If barge-in occurred within twenty milliseconds of the mark's execution, the code retrieves the index of the preceding movie under the assumption that the user was slow to react.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml"
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">

  <script src="movies.js"/>

  <form id="list_movies">
    <!-- fetch the current list of movies, and transform them into an array -->
    <data name="domMovies" src="getmovies.cgi"/>
    <var name="movies" expr="GetMovieList(domMovies)"/>
    <var name="movie_idx" expr="0"/>
    <var name="movie_id"/>
  
    <field name="mov">
      <prompt>
        Say the name of the movie.
      </prompt>
  
      <prompt count="2">
        Here's the list of movies. 
        To hear more about a movie, say 'tell me more'.
        <break time="500ms"/>
        <foreach item="movie" array="movies">
          <mark nameexpr="movie_idx++"/>
          <audio expr="movie.audio"><value expr="movie.tts"/></audio>
          <break time="500ms"/>
        </foreach>
      </prompt>
  
      <grammar type="application/srgs+xml" src="more.grxml"/>
      <grammar type="application/srgs+xml" src="movies.grxml"/>
  
      <catch event="nomatch">
        Sorry. I didn't get that.
        <reprompt/>
      </catch>
  
      <catch event="noinput">
        <reprompt/>
      </catch>
  
      <filled>
        <if cond="'more' == mov">
          <!-- user wants more detail -->
          <!-- assume no mark was executed -->
          <assign name="movie_idx" expr="0"/>
          <if cond="mov$.markname != undefined">
            <!-- alas, a mark was executed, so adjust movie_idx -->
            <if cond="mov$.marktime &lt;= 20">
              <!-- returns the id of the previous movie (or the first) -->
              <assign name="movie_idx" 
                expr="(mov$.markname &lt;= 1 ? 0 : mov$.markname-1)"/>
            <else/>
              <assign name="movie_idx" expr="mov$.markname"/>
            </if>
          </if>          
          <assign name="movie_id" expr="movies[movie_idx].id"/>
        <else/>
          <!-- user said a specific movie -->
          <assign name="movie_id" expr="mov"/>
        </if>
      </filled>    
    </field>

    <!-- 
     Given a movie id, fetch detail, and play it back.
     detail could be in a single wav file or in multiple files.
    -->  
    <block name="play_detail">
      <!-- GetMovieDetail returns an array of objects with properties audio and tts. -->
      <var name="details" expr="GetMovieDetail(domMovies, movie_id)"/>
      <foreach item="chunk" array="details">
        <audio expr="chunk.audio"><value expr="chunk.tts"/></audio>
      </foreach>
    </block>
  
  </form>
</vxml>

The following is a contrived XML document returned by getmovies.cgi. The user-defined GetMovieList and GetMovieDetail functions below are implemented to manipulate the DOM representation of its structure.

<?xml version="1.0" encoding="UTF-8"?>
<movies xmlns="http://www.example.org">
  <movie id="m0010">
    <title>
      <tts>the godfather</tts>
      <wav>godfather.wav</wav>
    </title>
    <details>
    <detail>
      <wav>directors/directed_by.wav</wav>
      <tts>directed by</tts>
    </detail>
    <detail>
      <wav>directors/coppola.wav</wav>
      <tts>francis ford coppola</tts>
    </detail>
    <detail>
      <wav>ratings/rated.wav</wav>
      <tts>rated</tts>
    </detail>
    <detail>
      <wav>ratings/r.wav</wav>
      <tts>r</tts></detail>
    <detail>
      <wav>pauses/300.wav</wav>
      <tts/>
    </detail>
    <detail>
      <wav>synopsis/m0010.wav</wav>
      <tts>a coming of age story about a nice italian boy</tts>
    </detail>
    </details>
  </movie>
  
  <movie id="m0052">
    <title>
      <tts>high fidelity</tts>
      <wav>high_fidelity.wav</wav>
    </title>
    <details>
      <!-- details omitted for the sake of brevity -->
    </details>
  </movie>
  
  <movie id="m0027">
   <title>
     <tts>raiders of the lost ark</tts>
     <wav>raiders.wav</wav>
   </title>
    <details>
      <!-- details omitted for the sake of brevity -->
    </details>
  </movie>
</movies>

The following is an implementation of the user-defined GetMovieList function:

// return an array of user-defined movie objects retrieved from the DOM
function GetMovieList(domMovies) {
  var movies = new Array();
  try {
    var nodeRoot = domMovies.documentElement;
    for (var i = 0; i < nodeRoot.childNodes.length; i++) {
      var nodeChild = nodeRoot.childNodes.item(i);
      if ("movie" != nodeChild.nodeName) {
        continue;
      }
      else {
        var objMovie = new Object(); 
        objMovie.id = nodeChild.getAttributeNS("http://www.example.org" "id");
        var nodeTitle = GetTitle(nodeChild);
        objMovie.audio = GetWav(nodeTitle);
        objMovie.tts = GetTTS(nodeTitle);
        movies.push(objMovie);
      }
    }
  }
  catch(e) {
    // unable to build movie list
    var objError = new Object();
    objError.audio = "nomovies.wav";
    objError.tts = "sorry. no movies are available."
    details.push(objError);
  }
  return movies;
}

function GetTitle(nodeMovie) {
  return GetChild(nodeMovie, "title");
}

function GetTTS(node) {
  return GetInnerText(GetChild(node, "tts"));
}

function GetWav(node) {
  return GetInnerText(GetChild(node, "wav"));
}

// perform a shallow traversal of the node referenced by parent 
// looking for the named node
function GetChild(parent, name)
{
  var target = null;
  for (var i = 0; i < parent.childNodes.length; i++) {
    var child = parent.childNodes.item(i);
    if (child.nodeName == name) {
      target = child;
      break;
    }
  }
  return target;
}

// Given a node, dig the text nodes out and return them as a string
function GetInnerText(node) {
  var s = "";
  if (null == node) {
    return s;
  }

  for (var i = 0; i < node.childNodes.length; i++) {
    var child = node.childNodes.item(i);
    if (Node.TEXT_NODE == child.nodeType || Node.CDATA_SECTION_NODE == child.nodeType) {
      s += child.data;
    }
    else if (Node.ELEMENT_NODE == child.nodeType) {
      s += GetInnerText(child);
    }
  }
  return s;
}

The following is an implementation of the user-defined GetMovieDetail function:

// get the details about the movie specified by id
function GetMovieDetail(domMovies, id) {
  var details = new Array();
  try {
    var nodeMovie = domMovies.getElementById(id);
    var nodeTitle = GetTitle(nodeMovie);
    var objTitle = new Object();
    objTitle.audio = GetWav(nodeTitle);
    objTitle.tts = GetTTS(nodeTitle);
    details.push(objTitle);
    var nodeDetails = GetChild(nodeMovie, "details");
    for (var i = 0; i < nodeDetails.childNodes.length; i++) {
      var nodeChild = nodeDetails.childNodes.item(i);
      if ("detail" == nodeChild.nodeName) {
        var objDetail = new Object();
        objDetail.audio = GetWav(nodeChild);
        objDetail.tts = GetTTS(nodeChild);
        details.push(objDetail);
      }
    }
  }
  catch(e) {
    // couldn't get movie details
    var objError = new Object();
    objError.audio = "nomovie.wav";
    objError.tts = "sorry. details for that movie are unavailable."
    details.push(objError);
  }

  return details;
}

When the interpreter queues the second <prompt> in the field named "mov", it expands the <foreach> element to the following:

<mark name="0"/>
<audio src="godfather.wav">the godfather</audio>
<break time="300ms"/>
<mark name="1"/>
<audio src="high_fidelity.wav">high fidelity</audio>
<break time="300ms"/>
<mark name="2"/>
<audio src="raiders.wav">raiders of the lost ark</audio>
<break time="300ms"/>

If the user chooses "The Godfather", when the interpreter executes the "play_detail" <block>, it expands the <foreach> element to the following:

<audio src="directors/directed_by.wav">directed by</audio>
<audio src="directors/coppola.wav">francis ford coppola</audio>
<audio src="ratings/rated.wav">rated</audio>
<audio src="ratings/r.wav">r</audio>
<audio src="pauses/300.wav"/>
<audio src="synopsis/m0010.wav">a coming of age story about a nice italian boy</audio>

7 Recording User Utterances While Attempting Recognition

Several elements defined in [VXML2] can instruct the interpreter to accept user input during execution. These elements include <field>, <initial>, <link>, <menu>, <record>, and <transfer>. VoiceXML 2.1 extends these elements to allow the interpreter to conditionally enable recording while simultaneously gathering input from the user.

To enable recording during recognition, set the value of the recordutterance property to true. If the recordutterance property is set to true in the current scope, the following three shadow variables are set on the application.lastresult$ object whenever the application.lastresult$ object is assigned (e.g. when a <link> is matched):

When these properties are set on the application.lastresult$ object, if an input item (as defined in section 2.3 of [VXML2]) has also been filled and has its shadow variables assigned, the interpreter must also assign recording, recordingsize, and recordingduration shadow variables for these input items, the values of which equal the corresponding properties of the application.lastresult$ object. For example, in the case of <link> and <menu>, since no input item has its shadow variables set, the interpreter only sets the application.lastresult$ properties.

Support for this feature is optional on <record>, and <transfer>. Platforms that support it set the aforementioned shadow variables on the associated form item variable and the corresponding properties on the application.lastresult$ object when the recordutterance property is set to true in an encompassing scope.

Like recordings created using the <record> tag, utterance recordings can be played back using the expr attribute on <audio>.

Like recordings created using the <record> tag, utterance recordings can be submitted to a document server via HTTP POST using the namelist attribute of the <submit>, <data>, and <subdialog> elements. The enctype attribute must be set to "multipart/form-data" [RFC2388], and the method attribute must be set to "post". To provide flexibility in the naming of the variable that is submitted to the document server, the interpreter must allow the utterance recording to be assigned to and posted via any valid ECMAScript variable.

In the following example, the dialog requests a city and state from the user. On the third recognition failure, the recording of the user's utterance is submitted to a document server.

<?xml version="1.0" encoding="UTF-8"?>
<vxml xmlns="http://www.w3.org/2001/vxml" 
  version="2.1"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">
  <form>
    <property name="recordutterance" value="true"/>

    <field name="city_state">
     <prompt>
      Say a city and state.
     </prompt>

     <grammar type="application/srgs+xml" src="citystate.grxml"/>

     <nomatch>
      I'm sorry. I didn't get that.
      <reprompt/>
     </nomatch>

     <nomatch count="3">
        <var name="the_recording" 
          expr="application.lastresult$.recording"/>
        <submit method="post" 
          enctype="multipart/form-data" 
          next="upload.cgi"
          namelist="the_recording"/>
     </nomatch>
    </field>  
  </form>
</vxml>

8 Adding namelist to <disconnect>

As described in section 5.3.11 of [VXML2], the <disconnect> element causes the interpreter context to disconnect from the user. VoiceXML 2.1 extends the <disconnect> element to support the following attribute:

The <disconnect> namelist and the <exit> namelist are processed independently. If the interpreter executes both a <disconnect> namelist and an <exit> namelist, both sets of variables are available to the interpreter context. The precise mechanism by which these variables are made available to the interpreter context is platform specific.

9 Adding type to <transfer>

As described in section 2.3.7 of [VXML2], the <transfer> element directs the interpreter to connect the caller to another entity. VoiceXML 2.1 extends the <transfer> element to support the following additional attribute:

Exactly one of the "bridge" or "type" attributes may be specified; otherwise an error.badfetch event is thrown.

As specified in 2.3.7 of [VXML2], the <transfer> element is optional, though platforms should support it. Platforms that support <transfer> may support any combination of bridge, blind, or consultation transfer types. Platforms supporting consultation transfer may optionally support bargein input modes of DTMF, speech recognition, or both, to cancel the call transfer attempt before the outgoing call is connected; bargein properties apply as normal. In addition, platforms supporting consultation transfer may optionally support the transferaudio attribute to specify the URI of an audio source to play while the transfer attempt is in progress and before far-end answer If the transferaudio attribute is not supported the behavior is the same as if it were not specified.

If the value of the type attribute is set to "bridge", the interpreter's behavior must be identical to its behavior when the value of the bridge attribute is set to "true". If the value of the type attribute is set to "blind", the interpreter's behavior must be identical to its behavior when the bridge attribute is set to "false". The behavior of the bridge attribute is fully specified in section 2.3.7 of [VXML2]. If the type attribute is specified and the bridge attribute is absent, the value of the type attribute takes precedence over the default value of the bridge attribute.

The bridge attribute is maintained for backwards compatibility with [VXML2]. Since all of the functionality of the bridge attribute has been incorporated into the type attribute, developers are encouraged to use the type attribute on platforms that implement it.

The connecttimeout attribute of <transfer> applies if the type attribute is set to "bridge" or "consultation".

The maxtime attribute of <transfer> applies if the type attribute is set to "bridge".

9.1 Consultation Transfer

The consultation transfer is similar to a blind transfer except that the outcome of the transfer call setup is known and the caller is not dropped as a result of an unsuccessful transfer attempt. When performing a consultation transfer, the platform monitors the progress of the transfer until the connection is established between caller and callee. If the connection cannot be established (e.g. no answer, line busy, etc.), the session remains active and returns control to the application. As in the case of a blind transfer, if the connection is established, the interpreter disconnects from the session, connection.disconnect.transfer is thrown, and document interpretation continues normally. Any connection between the caller and the callee remains in place regardless of document execution. For additional information on call transfers with consultation-like functionality see "AT&T Toll Free Transfer Connect" [ATT_50075], "MCI Enhanced Call Routing" [MCI_ECR], "ETSI Explicit Call Transfer" [ETSI300_369], and "SIP Attended Transfer" [SIP_EX].

Figure 1: Audio Connections during a consultation transfer: <transfer type="consultation"/>

The possible outcomes for a consultation transfer before the connection to the callee is established are:

Table 11: Consultation Transfer Outcomes Prior to Connection Being Established

Action	Value of form item variable	Event	Reason
caller disconnects		connection.disconnect.hangup	The caller hung up.
caller cancels transfer before outgoing call begins	near_end_disconnect		The caller canceled the transfer attempt via a DTMF or voice command before the outgoing call begins (during playback of queued audio).
callee busy	busy		The callee was busy.
network busy	network_busy		An intermediate network refused the call.
callee does not answer	noanswer		There was no answer within the time specified by the connecttimeout attribute.
---	unknown		The transfer ended but the reason is not known.

The possible outcomes for a consultation transfer once the connection to the callee is established are:

Table 12: Consultation Transfer Outcome After Connection Has Been Established

Action	Value of form item variable	Event	Reason
transfer begins	undefined	connection.disconnect.transfer	The caller was transferred to another line and will not return.

9.3 Example of a Consultation Transfer

The following example attempts to perform a consultation transfer of the caller to a another party. Prompts may be included before or within the <transfer> element. This may be used to inform the caller of what is happening, with a notice such as "Please wait while we transfer your call." The <prompt> within the <block>, and the <prompt> within <transfer> are queued and played before actually performing the transfer. After the prompt queue is flushed, the outgoing call is initiated. The "transferaudio" attribute specifies an audio file to be played to the caller in place of audio from the far-end until the far-end answers. If the audio source is longer than the connect time, the audio will stop playing immediately upon far-end answer.

Figure 2: Sequence and timing during an example of a consultation transfer

<?xml version="1.0" encoding="UTF-8"?>
<vxml version="2.1" 
  xmlns="http://www.w3.org/2001/vxml"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
  http://www.w3.org/TR/2007/REC-voicexml21-20070619/vxml.xsd">
<catch event="connection.disconnect.transfer">
   <!-- far-end answered -->
   <log> Connection with the callee established: transfer executed.</log>
</catch>

<form id="consultation_xfer">
   <block>
     <!-- queued and played before starting the transfer -->
     <prompt>
        Calling Riley.
     </prompt>
   </block>
   <!-- Play music while attempting to connect to far-end -->
   <!-- Wait up to 60 seconds for the far end to answer  -->
   <transfer name="mycall" dest="tel:+1-555-123-4567"
      transferaudio="music.wav" connecttimeout="60s" type="consultation">
     <!-- queued and played before starting the transfer -->
     <prompt>
        Please wait...
     </prompt>
     <filled>
        <if cond="mycall == 'busy'">
           <prompt>
             Riley's line is busy. Please call again later.
           </prompt>
         <elseif cond="mycall == 'noanswer'"/>
           <prompt>
             Riley can't answer the phone now. Please call
             again later.
           </prompt>
         </if>
      </filled>
   </transfer>
   <!-- submit call statistics to server -->
   <block>
      <submit namelist="mycall" next="/cgi-bin/report"/>
   </block>
</form>
</vxml>