An introduction to modular modeling and simulation with pythonpDEVS and the building-block library pythonpDEVS-BBL

ABSTRACTThe Discrete Event System Specification (DEVS) is a popular formalism devised by Bernard Zeigler in the late 1970s for modeling complex dynamical systems using a discrete event abstraction. At this abstraction level, a timed sequence of pertinent "events" input to a system (or internal timeouts) causes instantaneous changes to the state of the system. Main advantages of DEVS are its precise, implementation independent specification, and its support for modular composition. This tutorial introduces the Classic DEVS formalism in a bottom-up fashion, using a simple traffic light example. The syntax and operational semantics of Atomic (i.e., non-hierarchical) models are introduced first. Coupled (i.e., hierarchical) models are introduced to structure and couple Atomic models. We continue to actual applications of DEVS, with an example in performance analysis of queueing systems. This uses generator, queue, etc. components from our PythonPDEVS Building Block Library. All examples in the paper are presented using the language PythonPDEVS and its simulator, though this introduction is equally applicable to other DEVS implementations. We conclude with further reading on DEVS theory, variants, and tools.