Some Apple documents

Document Architecture

http://developer.apple.com/documentation/Cocoa/Conceptual/Documents/Documents.html

 

Pasteboard (note the sections on implementing copy/paste, specifically

cut)

http://developer.apple.com/documentation/Cocoa/Conceptual/CopyandPaste/CopyandPaste.html#//apple_ref/doc/uid/10000068

 

Undo Architecture

http://developer.apple.com/documentation/Cocoa/Conceptual/UndoArchitecture/UndoArchitecture.html#//apple_ref/doc/uid/10000010

 

Cocoa Event Handling

http://developer.apple.com/documentation/Cocoa/Conceptual/EventOverview/Introduction/chapter_1_section_1.html