AJAX and Drupal

I've found some post about AJAX and Drupal here at drupal.org and i have one question.
Is there something like a AJAX API to write AJAX based Drupal modules?

On my site learn-php/catalog you can find a AJAX based (Beta) Web Directory Drupal module. I used the SAXAX API from www.modernmethod.com to implement this little sample.
But in my opinion it would be much better if we have one API to implement AXAX fiunctionality in Drupal modules.