Automatic posting via code

Hi there!

Either there is already a plugin or I want to create one. I have an article on the server (either from a database, a text file or an email) and I want to post it to my blog by means of a plugin.

How difficult is it to create a posting by PHP alone, automatically? Complete with all notifications, etc., as if I created it by hand? Or is it easier to write the new article to an RSS file on the same server and let WordPress publish that RSS feed?

Thanks for your help!