Bret Victor's treatise on a different design paradigm ("Magic Ink") included this gem. It is a representation of a train schedule; each colored line is a train. Time is left-to-right, destinations are top to bottom. Slopes indicate the speed of the train; intersections of train lines at times and destinations show arrival times.
Design Maps The diagram shows a task with levels of design assigned to levels of priority. Task: Assign options to users Requirements (cake): Assign basic DB options Enhancements (frosting): Assign detailed DB options Embellishments (sprinkles): Create user groups for options Very interesting approach. If you're a user experience professional, listen to The UX Blog Podcast on iTunes.