In most situations, the CVP Subdialog Start element (see CVP Subdialog Start) should be used instead of this one, to offer full compatibility with ICM. However, there is one exception to this. If the voice application will only be called by a Subdialog Invoke element (that is, never by ICM), then the Subdialog Start and Subdialog Return elements may be used instead.

Data can be passed to the VoiceXML application either as HTTP parameters or VoiceXML parameters (using the <param> tag). In the first case (that is, as HTTP parameters), Call Services will automatically create session data using the name of the data received. In the second case (that is, as VoiceXML parameters), the Subdialog Start element must be configured appropriately in order for the data to be available as element or session data for the duration of the call session. For each data passed as a VoiceXML parameter, the repeatable Parameter setting must be configured with the same exact name as the data.