Simulation, used as a technical term, means experimentation with models that have time-varying behavior. These types of models are also called dynamic models. Therefore, a concise and generic definition of simulation is experimentation with dynamic models. Several types of simulation exist, leading to several specialized conceptions of it. Schriber perceives simulation from a specialized point of view. According to him, “Simulation is just one of the techniques in the field of operations research and management science (OR/MS)” (p.3).
In vocational training in simulation, one can get useful and usable information about simulation. This contrasts with the approach taken in simulation education, in which introducing an advanced field such as simulation from the viewpoint of a language is to be avoided, especially if we remember the adage that for somebody who holds a hammer, all things look like nails. Depending on one’s taste, it is possible to use this book for either training or education in simulation. In the latter case, one might choose to supplement it with another text to provide background in modeling and in simulation of discrete-change models.
This book consists of 17 chapters, three appendices, a list of references (covering most of the other books on GPSS), and author and subject indices. The book comes with two diskettes (3.5–inch and 5.25–inch) for a PC or compatible. The student gets a diskette containing GPSS/H, licensed by Wolverine Software Corporation. Those who teach from the book may contact the author directly to receive instructional support material. The chapter titles are
Perspectives on Simulation and GPSS/H
Transactions: Their Creation, Movement, and Destruction
More About Transaction Creation and Movement
How Transactions are Managed by GPSS/H
Additional Test-mode Capabilities
Fundamental Modeling of Single Servers
More About How Transactions Are Managed by GPSS/H
More Imaginative Modeling of Single Servers
Gathering Information About Transactions
Expanding the Set of Test-mode Capabilities
Modeling Groups of Identical Servers
Additional Blocks for Controlling Transaction Direction and Timing
Modeling with Nonuniform Probability Distributions
Statistical Experiments with Single-system Models
The Use of Antithetic Variates in Single-system Modeling
Statistical Experiments with Models of Competing Alternatives
Epilogue
The appendices provide information about Installing and Checking Out Student DOS GPSS/H
Commands and Options for Running GPSS/H Models Under DOS
Solutions to Selected Exercises
The first chapter is an introduction to simulation and GPSS/H. Chapters 2 through 16 provide in-depth knowledge about GPSS/H. Several aspects of transactions are covered in detail in chapters 2, 3, 4, 5, 7, 9, and 12. Chapter 17 starts with the following clarification: “GPSS/H provides over 65 types of Blocks, 35 types of Control Statements, 20 types of Compiler Directives, and 15 types of Report Statements, for a total in excess of 135 types of statements. Only a subset of this rich collection of GPSS/H capabilities has been introduced in this book. The purpose of this Epilogue is to survey some of the GPSS/H capabilities not covered in the book and to suggest how those interested can proceed in the further study of GPSS/H” (p. 360).
The author describes the syntactic details of how to program in GPSS/H rather than how to model and express the model in GPSS. (The latter was the approach of an early book on GPSS by Bobillier et al. [1].) For example, “Bug Clinic” sections Schriber provides in several chapters consist of “exercises involving models that contain errors of one kind or another. The response of GPSS/H to those errors can be determined by carrying out simulations with these models. In doing these exercises, it will be useful to distinguish between Compile-Time and Execution-Time Error Messages” (p. 58).
Until a knowledge-based simulation environment is available for GPSS, one has to teach these details to students. In the future, a knowledgeable environment may assist the user in the specification phase and explain why a certain specification cannot be accepted, freeing the human mind for more creative tasks of problem solving rather than making this type of training a necessity. If and when this becomes a reality, I am sure Schriber can teach such advanced systems with equal clarity and step-by-step instructions. His book is a good starting point for those interested in learning GPSS/H.
