Docs for required versus optional

Consider the list of required JS files for Dialog:
http://docs.jquery.com/UI/Dialog
* ui.core.js
* Optional, ui.draggable.js
* Optional, ui.resizable.js
I read this as: You must use ui.core.js and that's it. However, you
can't run anything w/o also including ui.dialog.js
Was that meant to be implied?