Regarding xml:lang in prompts

Hi,
 
I have a query regarding language identification for playing of prompts.

Consider an application execution scenario as given below:
 
Root document:
<?xml version="1.0" encoding="GB2312" ?>
<vxml version="2.0" xml:lang="zh-CN">
    ......
    <catch>
        <prompt> HELP MESSAGE IN CHINESE, WRITTEN IN GB2312 FORMAT </prompt>
        <reprompt/>
    </catch>
</vxml>          
 
Leaf document:
<?xml version="1.0" encoding="UTF-8" ?>
<vxml version="2.0" xml:lang="en-US">
    ......
    <field>
          ....Some error gets generated while collecting the <field>...
    </field>
    .....
</vxml>
 
Here, as interpretation happens in the leaf document, an event is generated,
for which the event handler is picked up from root document and executed
as-if-by-copy in the leaf document. Here, the catch handler has a prompt
which has some content in one language format, which is different from the
current document's language format. So, when the prompt within the catch is
processed and queued for play, what should be the value of the language
parameter, if a play command has to be issued to the underlying platform?
 
Thanks
Rajesh