June 24, 2011, 12:58 p.m.
posted by demx
Organizing Participants on a Timing Diagram
Where you arrange participants on a timing diagram does not at first appear to be very important. However, as you add more details to your diagram in the form of events and timing information, you'll soon discover that the place where a participant is located on the timing diagram can cause problems if you haven't thought about it carefully enough (see Figure).
The bottom diagram is harder to read, and details are beginning to obscure one another
If you're lucky and you already have a sequence diagram for an interaction, then there is an easy rule of thumb to get you started when arranging participants for the first time on a timing diagram. Simply take the order of the participants as they appear across the top of the page on a sequence diagram and flip the list of participant names 90 degrees counterclockwise, as shown in Figure. If your sequence diagram is well-organized, then you should now have a good candidate order for placing the participants on your timing diagram.
Rotating a sequence diagram's major participant's 90 degrees counterclockwise is an easy way to get an initial placement for your timing diagram's participants