> For the complete documentation index, see [llms.txt](https://docs.plumvoice.com/dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.plumvoice.com/dev/voicexml/tags/param-tag.md).

# \<param>

## \<param> <a href="#param" id="param"></a>

The `<param>` element is used to specify values that are passed to subdialogs.

### Attributes

<table><thead><tr><th width="166.33333333333331">Name</th><th width="151">Data type<select><option value="c9416a7f82664d52bb89ce66fe71fb66" label="String" color="blue"></option><option value="6f8c4a3144a445339edac37dfd8aed38" label="Integer" color="blue"></option><option value="c116ac70255e47ecab3666053f729e18" label="Boolean" color="blue"></option></select></th><th>Description</th></tr></thead><tbody><tr><td>name</td><td><span data-option="c9416a7f82664d52bb89ce66fe71fb66">String</span></td><td>The name to be associated with this parameter when subdialog is invoked.</td></tr><tr><td>expr</td><td><span data-option="c9416a7f82664d52bb89ce66fe71fb66">String</span></td><td>An expression that computes the value associated with name.</td></tr><tr><td>value</td><td><span data-option="c9416a7f82664d52bb89ce66fe71fb66">String</span></td><td>Associates a literal string value with name.</td></tr><tr><td>valuetype</td><td><span data-option="c9416a7f82664d52bb89ce66fe71fb66">String</span></td><td><p>(defaults to “data”) Either data or ref; used to indicate to an object if the value associated with name is data or a URI (ref).</p><p></p><p>This is not used for <code>&#x3C;subdialog></code> since values are always data.</p></td></tr></tbody></table>

### Notes

The `<param>` elements of a `<subdialog>` specify the parameters to pass to the subdialog. These parameters must be declared in the subdialog using `<var>` elements; it is a semantic error to attempt to set a form item variable or an undeclared variable using `<param>`.&#x20;

When a subdialog initializes, its variables are initialized in document order to the value specified by the `<param>` element with the corresponding name. The parameter values are computed by evaluating the `<param>` expr attribute in the context of the `<param>` element. An expr attribute in the `<var>` element is ignored in this case.

If no corresponding `<param>` is specified to `<var>` element, an expr attribute is used as a default value, or the variable is undefined if the expr attribute is unspecified as with the regular `<form>` element.

### Example

```markup
<?xml version="1.0"?>
<vxml version="2.0">
  <!-- form dialog that calls a subdialog -->
  <var name="myname" expr="'Jane Doe'"/>
  <form>
    <subdialog name="result" src="#getdriverslicense" namelist="myname">
      <!-- This will send the variable "birthday" to the -->
      <!-- subdialog "#getdriverslicense". -->
      <param name="birthday" expr="'February 10th, 1970'"/>
      <filled>
        You entered <value expr="result.drivelicense"/>.
        <submit next="http://nonexistent.domain.com/process.pl"
          method="post"
          namelist="result.drivelicense birthday"/>
      </filled>
    </subdialog>
  </form>
  <!-- subdialog to get drivers license -->
  <form id="getdriverslicense">
    <!-- In order to receive parameters sent from a "subdialog" tag, -->
    <!-- the parameters must be declared within the subdialog with the -->
    <!-- exact same name. -->
    <var name="birthday"/>
    <field name="drivelicense" type="digits">
      <prompt>
        <value expr="myname"/>,
        your birthdate is: <value expr="birthday"/>.
        Please say your driver's license number.
      </prompt>
      <filled>
        <return namelist="drivelicense"/>
      </filled>
    </field>
  </form>
</vxml>
```

The output of the above script would be:

> Computer: Jane Doe, your birthdate is: February 10th, 1970.\
> Computer: Please say your driver's license number.\
> Human: One two three four five six seven eight nine.\
> Computer: You entered one hundred twenty-three million, four hundred fifty-six thousand, seven hundred eighty-nine.\
> (continues on to processing form…)

### Child Tags

None

### Parent Tags

[\<subdialog>](/dev/voicexml/tags/subdialog-tag.md)