Hi Petr,
it is a good idea to have one (optional) field for sorting here; but I have also one hint how you CAN control the sequence already, by using hierarchical mappings from root structure.
1. In "Select Source Structure", enter "SPACE" for the root structure
2. In "Assign Destination Structure", insert three structure mappings 10/20/30 with destination structure "SPACE"
3. In "Define Field Mapping" of structure mapping 10, enter the structure which should be mapped first as indirect mapping (using "Field in Destination Structure" and "Sub-Table")
4. Define your "real" structure mapping as usual, but set the flag "Indirect Mapping" in "Assign Destination Structure"
Then AIF will execute your structure mappings in the defined sequence.
Best regards,
Thomas Elsässer (AIF Development Team)