Pre-loading Form fields and Collecting User Form Entries

Hello!

I am new to XForms and have a basic question to ask.

I have a 3-tier web based application that would benefit from XForms. It 
basically queries for data from a remotely located database, and allows 
certain fields in the queried data to be modified and sent back as an 
update to the database.

The queries retrieve the data via a particular XML message, the updates 
are however dispatched using a similar but different XML message. 

The question is, how do I pre-load my form fields from the initial message 
received from the back-end, and send the updates through a different 
message. It seems as if I need two data models instances, one for 
pre-loading the fields, and a second instance for capturing the user's 
edits for dispatched to the back-end.

Any thoughts or ideas you have would be greatly appreciated.

Thanks
-- Ade Lucas