Epilogue

This book presented numerous results on production systems. Some are simple and, from our point of view, elegant. Many are more involved and aesthetically less attractive. All of them, we believe, are practical. What is it that makes them possible? What are the common themes in the foundation of these results? Three answers can be given to these questions:

1. The possibility of exact analysis of two-machine systems and a certain level of machine decoupling, afforded by buffering, allow for the aggregation procedures, which, in the final account, describe the systems at hand in the Markovian case.

2. Filtering properties, also afforded by buffering, eliminate the dependence of various performance measures on higher order moments of random phenomena that affect systems' behavior. Only the first two moments are of importance. Moreover, these two moments affect the behavior not independently but in conjunction with each other – in the form of the coefficient of variation. This allows for the analysis of systems in the non-Markovian case.

3. The sensitivity of the throughput to machine and buffer parameters is closely related to machines' blockages and starvations. This places the probabilities of blockages and starvations at the center of continuous improvement of both Markovian and non-Markovian systems, which is the foundation of the main practical outcome of this work – Measurement-based Management of production systems.

These simplifying phenomena allow us to conclude this volume with a paraphrase of the well-known maxim attributed to Albert Einstein, Nature is complex but not evil:

Production systems are complex but not evil.