BME-cat importer to db

It’s the first project for me on ruby on rails.
I want to write a XML importer to database. But i have several question
1)for my purpose of creating importer should I have an example file with
full-filled XML-data? (in the case creating all lines in the different
2) do you an example of XML-BME-cat file ?
3) do you have specification on english. (I have on German)
4) can you give me advice how to create database structure in such
projects??(open specification and manually adding new line to each table
or there is another way?)

  1. how do you solve such project step-by-step?