This is the first implementation I have made for the VXML Parser :
1- Validate XML
2- Validate VXML 2.0 Tags
3- Validate that VXML tag is present in the beginning of the vxml document with the version 2.0
4- Validate VXML elements fonctionality
5- Validate VXML attributes in vxml document

If you need more informations or suggestion contact me by email, sorry if it is not well commented

Download :
http://www.ziddu.com/download/7293005/vxmlparser-2002-10-01.zip.html