Using xml files for a web project.

Almost ... if base_url('assets/...') is publically accessible, you are exposing your data, which is not good.
A better practice is to map your document root to your "public" folder, put index.php inside that, and to keep any XML data in a separate folder inside the project (or even elsewhere on your server).

Eg.
project
- application
- data
- XML ...
- public
- assets/images, css, etc
- index.php
- system