Finite & Deterministic Discrete Event System Specification - History

History

FD-DEVS was originally named as ``Schedule-Controlable DEVS`` and designed to support verification analysis of its networks which had been an open problem of DEVS formalism for 30 years. In addition, it was also designated to resolve the so-called ``OPNA`` problem of SP-DEVS. From the viewpoint of Classic DEVS, FD-DEVS has three restrictions

  1. finiteness of event sets and state set,
  2. the lifespan of a state can be scheduled by a rational number or infinity, and
  3. the internal schedule can be either preserved or updated by an input event.

The third restriction can be also seen as a relaxation from SP-DEVS where the schedule is always preserved by any input events. Due to this relaxation there is no longer OPNA problem, but there is also one limitation that a time-line abstraction which can be used for abstracting elapsed times of SP-DEVS networks is no longer useful for FD-DEVS network . But another time abstraction method which was invented by Prof. D. Dill can be applicable to obtain a finite-vertex reachability graph for FD-DEVS networks.

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