Did you look at this? http://docs.elgg.org/wiki/REST_API and http://elggnews.com/pg/blog/cash/read/120/new-and-improved-web-services-api-in-elgg-17

These are fairly inclusive for anything you might want to do...the rest is just your imagination :)

hey Brett

thanks for your reply. the blog post was indeed instructive, but I've one more thing to ask. I got the concept of exposing functions, but where exactly should those .php files be saved in the file system, and what other preparations i need to make before being able to use the api.

thanks

Just put the functions in your start.php file or a file included by it...