XML DB file into RDB ><!!

You can use either XmlSerializer or XmlReader. If you need all the data in memory to be processed in memory, then use XmlSerializer. If you need to just read the XML file and write it out as it is read without having to access other parts of the data that is in very different locations then use XmlReader. The choice might not be very obvious but I don't know the details of the data. You might be able to use the output database to refer to as you build the outpur; for example, if you have a table of subjects and a table of authors and a table of publishers then you can build those tables first and then use the database to insert publications and use the existing tables to relate the subjects, authors and publishers to the publications.

There are probably utilities you can use without writing any code. You could process the data into a database and then process it more as needed.