PP1: simple PingPong model
PP2: PingPong model w/ hit count and choice point
PP3: PingPong model w/ timers
PP4: command line arguments and random number generator
PP5: client (pinger)/server (ponger) relationship: client sends two requests 'inc(x)' and 'doub(x)' in alternating fashion; server responds with 'result(y)'
PP6: illustration of 'hidden state' anti-pattern: 'Client' keeps track of which message to send next via flag ('waitingForInc')
PP7: illustration of composite states and timers