In an electronic file system, preview information is provided to the user during a drag operation of a selected object onto a target object. The information indicates what type(s) of action is to be taken should the selected object be dropped onto the target object. The action(s) to be taken may depend...http://www.google.de/patents/US7650575?utm_source=gb-gplus-sharePatent US7650575 - Rich drag drop user interface
