Hi Thierry,
I'm not sure I understand your question. Are you asking "how we bind the text from a secondary data source to the main DOM"? Or, are you asking "how do we set default data using template.xml"? These are different questions.
For the first: you can bind a dropdown to your main DOM (data source) and specify a secondary data source for lookup.
For the second: you can edit the default sample data from within the designer. Go to Tools->Form Options->General->Edit Default Values.
Hope this helps!
Patrick
PS> for your signature, you should probably change "Think it" to "Think about it" but sounds a little threatening if you ask me.
PPS> for my signature, I'd say something like "life is short, don't forget to inhale" :)
Patrick Halstead
Project Manager at Qdabra