WoW addons

Oh, it'd be hefty to make a WoW addon. I'm thinking: centered ragebar and a good marker for Slam procs. (edit: and indications for WW, BT out of cooldown)

So, what gives?

1. Apparently, addons are placed in {InstallationDir}/Interface/AddOns/MyCoolAddOn

2. (At least) Three (?) files define the addon:

1. A .toc file. A table of contents sort of thing.
2. A .xml file defining various UI objects. GUI parts are (it seems) orchestrated by xml files. Much like in Java, where awt or swing object have to be created and resized and fontisized and registered with ActionListeners and such, except it's done in xml. Sort of.
3. A .lua. A lua script file with code, defining the various callbacks (event handlers) tied to (registered with) the objects/classes defined in the xml file.

Except for lua, of course, there does not seem to be an offical listing of syntax/coding rules / supported xml tags. I wonder how the first addon makers got by. Were they secretly given info by Blizzard in order to start some kind of viral information spreading on the subject? Or how the heck did they do it? It's like breaking iPhones - I am clueless as to how to start.

(altho reverse engineering addons would be much simpler I guess since Blizzard offical "addons" are available... hmmm)