Real Time and Resource Overload Language

This pattern language merges the Traffic Congestion pattern language from PLoP-99 with the real time patterns in the 4ESS(R) collection as well as in Gerard Meszaros' pattern language for improving the capacity of reactive systems presented in PLOPD-2 [Mesz]. A system that reacts to externally provided stimuli might receive more stimulus than it can handle at any given time. When this "overload" situation occurs the system must be able to deal with it somehow. Many systems respond by ceasing all work, i.e., locking up or crashing. A well-designed system is able to handle the overload and respond gracefully to the excess stimuli. This system might have somewhat reduced capabilities during the transition, but it will correctly handle much of the work presented to it, and when stimuli levels return to normal, it can resume full functionality with minimal involvement. These patterns assume that the basics of a fault tolerant architecture exist. For example, the Minimize Human Intervention pattern language [ACGH+] has guided system design so that it will automatically respond to anomolous events.