It's exactly my problem.

The nodes are the same (<E1EDK02 SEGMENT="1"> in the header of invoice for example), but the information about type of field are stored in the fields QUALF

QUALF = 009 = InvoiceNumber

QUALF = 001 = OrderNumber

The comments are not inluded in the original file, I aded it to example only for better udersunderstanding structure of xml.