Documentation for on-line access

I'm the author of Astroplanner (http://www.astroplanner.net [1]). Previous versions of this application (from many years ago) would access AAVSO info by means of downloading text files from the AAVSO website, submitting observations via e-mail, and so on. Unfortunately none of that works any more. I'm about to update my application to support AAVSO observers, but I can't seem to find any API information for accessing the AAVSO databases.

Do such APIs exist? Looking over this forum I'm guessing they must. Does one access the data via SQL or via HTTP GET commands? Both methods seem to be hinted at.

Any information gratefully received.

Paul Rodman