IDOC-XML to IDOC FILE

Hi,

My scenario is IDOC to XI to IDOC FILE. I read through the HOW TO CONVERT IDOC-XML to IDOC FILE. They execute ABAP mapping to do this but they haven't specified the target structure. The source would obviously the idoc metadata but what would be the target structure. Here we are trying to generate a flat IDOC file ( not XML ) so my question here again is what should be the target structure in INTERFACE MAPPING?