6. The method of claim 1 wherein the plurality of first graphical affordances are arrows including heads and tails, and the heads and tails of at least two of the arrows are located at the parent and child lifelines.
7. The method of claim 6 wherein the message view window includes one or more gutter areas configured to represent parent or child components for which no lifelines are included, and a head or a tail of a first arrow is located at the one or more gutter areas.