A Simulator for NSA-DEVS in Matlab

Abstract

The PDEVS formalism is widely used for the description and analysis of discrete event systems. But PDEVS has some drawbacks in modeling Mealy behavior. A revised version (RPDEVS) has been invented to resolve them, but it has problems of its own, mainly because its complicated simulator structure. The recently proposed NSA-DEVS scheme tries to unite the advantages of both formalisms by using infinitesimal time intervals.To further substantiate this claim we describe an abstract simulator for NSA-DEVS, implement it in Matlab and simulate a simple queue-server system. This shows that NSA-DEVS combines the Mealy-like model description of RPDEVS with the simple simulator structure of PDEVS, making it a promising approach to implement an improved modeling and simulation system.

Implementing Standard Examples with NSA-DEVS

“…The abstract NSA-DEVS simulator uses the same structure of modules and messages as in PDEVS, but it implements the input delays and the Mealy-like behaviour. Its details, the differences to the PDEVS simulator and an implementation in Matlab can be found in [5].…”

“…To analyse the behaviour of this model in detail, we will retrace the simulator procedures. Generally, when an input value arrives at time t = 1 at a Mealy-like component with a time delay τ ∈ * R, its simulator module S and the coordinator C of its enclosing coupled component perform the following steps [5]:…”

“…The NSA-DEVS simulator that is described in [5] has no intrinsic output possibilities. Instead it uses an atomic component ToWorkspace that can be connected to an output port and copies the incoming values to a global output variable, which can be plotted or analysed after the simulation run.…”

“…The formal description of all these models is straighforward. Using the Matlab-based NSA-DEVS simulator from [5] the complete model is easily implemented and run.…”

“…To this end it introduces delay times at all inputs and forbids transitory states, i. e. states with a lifetime of zero. This allows to retain the mealy-type behaviour of RPDEVS, but makes the definition of an abstract simulator [5] much simpler than the corresponding simulator of RPDEVS [6].…”