State machine diagram maye useful from time to time. Object diagrams are sometimes great illustrations of how data is structured. I specifically recommend obj

State machine diagram maye useful from time to time. Object diagrams are sometimes great illustrations of how data is structured. I specifically recommend object diagrams, not class diagrams for that. If you are learning unfamiliar system just by reading the code and making user interactions, its easy to loose track what is recorded where. Collecting your observations on a diagram you draw gradually will help to acumulate details and build a clear picture. Maintaining several simple object diagrams for main usage scenarious may help future newcomer developers to quickly grasp the implementation backbone.