[Lizard]

Some of this info is already available through Finder, as follows:

set my_file_path to ""
tell application "OmniGraffle Professional 5"
	set my_file_path to path of front document
end tell

tell application "Finder"
	if my_file_path is not "" then
		set my_file to (POSIX file my_file_path) as alias
		properties of my_file
	end if
end tell