A Distributed Simulation System to Evaluate Reactive Schedulers

This document presents what reactive scheduling is and lays out simulation as a method for testing and evaluating a reactive scheduler. In the project REFRESH (a Reusable and Extendible Framework for REactive ScHeduling), a reactive scheduler is developed and a simulation environment is built to evaluate this reactive scheduler. The process of developing the simulation environment is described in this document. The simulation environment consists of different software agents which are distributed over one or more computers, each of the agents playing the role of one element of the “supply chain”. In addition to these agents, a manager agent and an applet are implemented to control the simulation and display simulation results. The agents communicate using mechanisms available from the Internet (for example, the TCP/IP protocol). It is shown how the results of several simulation runs can be evaluated and compared. To evaluate the performance of a reactive scheduler, the criteria “response time”, “fulfilling due dates and preferred dates”, “schedule robustness” and “shop floor nervousness” are measured. The implementation is platform-independent as far as possible and available in the Internet, so that anyone can test his own reactive scheduler and, eventually, evaluation results of different reactive schedulers can be compared.