ui.core.js API? Looking for core documentation...

ui.core.js API? Looking for core documentation...

So I am looking for some documentation (but can't seem to find it) concerning the "core" functionality included with jQuery UI (the functionality available when considering zero plugins, widgets or any other form of external file). Are these features enumerated anywhere in an atomic fashion? I have noticed that if I visit the individual pages of some of the interactions, they state the dependencies, but that is kind of user unfriendly way to go about it. Essentially, I am looking to see what sort basic functionality ui.core.js provides.
Also, why is it that "droppable" interaction requires ui.draggable.js, however, the "draggable" interaction does not. This is most confusing. And it appears that there is a ui.droppable.js, and yet the "droppable" documentation does not list said file as a dependency. So, the "droppable" interaction requires ui.draggable.js, but it does NOT require ui.droppable.js?!? My head hurts...