Access to Drupal data in an external PHP application : plain PHP or a minimum set of Drupal functions can be loaded ?

I want to build a lightweight PHP front-end to process some of the data in my Drupal database.

- Should I simply develop it in plain PHP and directly query the Drupal MySQL database ?
- Is there a way to load a minimal set of Drupal functions that would let me do this ?

Basically I need to select nodes on certain criteria including various CCK fields and location, and get the node title.

As I'm not very used to Drupal developing, I'd rather try the plain PHP approach, also because I suspect it the load on the server could be very reduced if I use only the minimal things needed, but not sure.

What do you think ?

Thanks