SIP NOTIFY and VoiceXML

Hi,

There are quite a few of SIP-enabled VoiceXML browsers on the market.

It is natural to use VoiceXML to drive the behaviour of a SIP user
agent. Now SIP provides the SUBSCRIBE-NOTIFY mechanism, how does
VoiceXML and SIP NOTIFY tie together?

Specifically, is there any standard way to write a VoiceXML script that
generates a SIP NOTIFY message? Which VoiceXML tags should one use? I am
thinking of a VoiceXML application that requires to send out some
application specific SIP NOTIFY message.

Any idea? Thank you.

Tony Cheung