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Wiley Series in Operations Research and Management Science

Operations Research and Management Science (ORMS) is a broad, interdisciplinary branch of applied mathematics concerned with improving the quality of decisions and processes and is a major component of the global modern movement towards the use of advanced analytics in industry and scientific research. The Wiley Series in Operations Research and Management Science features a broad collection of books that meet the varied needs of researchers, practitioners, policy makers, and students who use or need to improve their use of analytics. Reflecting the wide range of current research within the ORMS community, the Series encompasses application, methodology, and theory and provides coverage of both classical and cutting edge ORMS concepts and developments. Written by recognized international experts in the field, this collection is appropriate for students as well as professionals from private and public sectors including industry, government, and nonprofit organization who are interested in ORMS at a technical level. The Series is comprised of four sections: Analytics; Decision and Risk Analysis; Optimization Models; and Stochastic Models.

Advisory EditorsOptimization Models
Lawrence V. Snyder, Lehigh University
Ya‐xiang Yuan, Chinese Academy of Sciences

Founding Series Editor
James J. Cochran, University of Alabama


Analytics
Yang and Lee • Healthcare Analytics: From Data to Knowledge to Healthcare Improvement

Attoh‐Okine • Big Data and Differential Privacy: Analysis Strategies for Railway Track Engineering

Kong and Zhang • Decision Analytics and Optimization in Disease Prevention and Treatment

Forthcoming Titles

Dai • Handbook of Healthcare Analytics: Theoretical Minimum for Conducting 21st Century Research on Healthcare Operations

Decision and Risk Analysis
Barron • Game Theory: An Introduction, Second Edition

Brailsford, Churilov, and Dangerfield • Discrete‐Event Simulation and System Dynamics for Management Decision Making

Johnson, Keisler, Solak, Turcotte, Bayram, and Drew • Decision Science for Housing and Community Development: Localized and Evidence‐Based Responses to Distressed Housing and Blighted Communities

Mislick and Nussbaum • Cost Estimation: Methods and Tools

Forthcoming Titles
Aleman and Carter • Healthcare Engineering

Optimization Models
Ghiani, Laporte, and Musmanno • Introduction to Logistics Systems Management, Second Edition

Bozorg‐Haddad • Meta‐heuristic and Evolutionary Algorithms for Engineering Optimization

Baker and Trietsch • Principles of Sequencing and Scheduling, Second Edition

Forthcoming Titles
Smith • Learning Operations Research Through Puzzles and Games

Tone • Advances in DEA Theory and Applications: With Examples in Forecasting Models

Stochastic Models
Ibe • Random Walk and Diffusion Processes

Forthcoming Titles
Donohue, Katok, and Leider • The Handbook of Behavioral Operations

Matis • Applied Markov Based Modelling of Random Processes

Principles of Sequencing and Scheduling


Second Edition


Kenneth R. Baker and Dan Trietsch






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Preface

This textbook provides an introduction to the concepts, methods, and results of scheduling theory. It is written for graduate students and advanced undergraduates who are studying scheduling, as well as for practitioners who are interested in the knowledge base on which modern scheduling applications have been built. The coverage assumes no background in scheduling, and for stochastic scheduling topics, we assume only a familiarity with basic probability concepts. Among other things, our first appendix summarizes the important properties of the probability distributions we use.

We view scheduling theory as practical theory, and we have made sure to emphasize the practical aspects of our topic coverage. Thus, we provide algorithms that implement some of the solution concepts we describe, and we use spreadsheet models where appropriate to calculate solutions to scheduling problems. Especially when tackling stochastic scheduling problems, we must balance the need for tractability and the need for realism. Thus, we stress heuristics and simulation‐based approaches when optimization methods and analytic tools fall short. We also provide many examples in the text along with computational exercises among our end‐of‐chapter problems.

Coverage of the Text

The material in this book can support a variety of course designs. An introductory‐level course covering only deterministic scheduling can draw from Chapters 1–5, 8–10, 12–14, and 16–17. A one‐quarter course that covers both deterministic and stochastic topics can use Chapters 1–11 and possibly 15. Our own experience suggests that the entire book can support a two‐quarter sequence, especially with supplementary material we provide online.

The book contains two appendices. The first reviews the salient properties of well‐known probability distributions, as background for our coverage of stochastic models. It also covers selected topics on which some of our advanced coverage is based. The second appendix includes background derivations related to the “critical ratio rule,” which arises frequently in safe scheduling models.

Our coverage is substantial compared with that in other scheduling textbooks, but it is not encyclopedic. Our goal is to enable the reader to delve into the research literature (or in some cases, the practice literature) with enough background to appreciate the contributions of state‐of‐the‐art papers.

For the reader who is interested in a more comprehensive link to the research literature than our text covers, we provide a set of online Research Notes. The Research Notes represent unique material that expands the book’s coverage and builds an intellectual bridge to the research literature on sequencing and scheduling. In organizing the text, we wanted to proceed from simple to complex and to maintain technological order. As much as possible, each new result is based only on previous coverage. As a secondary guiding principle, the text minimizes any discussion of connections between models, thus keeping the structure simple. Scheduling theory did not develop along these same lines, however, so research‐oriented readers may wish to look at the bigger picture without adhering to these principles with the same fidelity. One purpose of our Research Notes is to offer such a picture. Another purpose is to provide some historical background. We also mention open research questions that we believe should be addressed by future research. Occasionally, we provide more depth on topics that are not sufficiently central to justify inclusion in the text itself. Finally, for readers who will be reading research papers directly from the source, we occasionally need to discuss topics that are not crucial to the text but arise frequently in the literature.

Historical Background

This book is an updated version of Baker’s text, so some historical background is appropriate at the outset. Introduction to Sequencing and Scheduling (ISS) was published by John Wiley & Sons in 1973 and became the dominant textbook in scheduling theory. A generation of instructors and graduate students relied on this book as the key source of information for advanced work in sequencing and scheduling. Later books stayed abreast of developments in the field, but as references in journal articles would indicate, most of those books were never treated as fundamental to the study of scheduling.

Sales of ISS slowed by 1980, and Wiley eventually gave up the copyright. Although they found a publishing house interested in buying the title, Baker took back the copyright. For several years, he provided generous photocopying privileges to instructors who were still interested in using the material, even though some of it had become outdated. Finally, in the early 1990s, Baker revised the book. The sequel was Elements of Sequencing and Scheduling (ESS), self‐published in 1992 and expanded in 1995. Less encyclopedic than its predecessor, ESS was rewritten to be readable and accessible to the student while still providing an intellectual springboard to the field of scheduling theory. Without advertising or sales reps, and without any association with a textbook publishing house, ESS sold several hundred copies in paperback through 2007. Another generation of advanced undergraduate and graduate students used the book in courses, while other graduate students were simply assigned the book as a required reading for independent studies or qualifying exams. Current research articles in scheduling continue to cite ISS and/or ESS as the source of basic knowledge on which today’s research is being built.

Perhaps the most important topic not covered in ESS was stochastic scheduling. With the exception of the chapter on job shop simulations, almost all the coverage in ESS dealt with deterministic models. In the last 15 years, research has focused as much on stochastic models as on deterministic models, and stochastic scheduling has become a significant part of the field. But traditional approaches to stochastic scheduling have their limitations, and new approaches are currently being developed. One important line of work introduces the notion of safe scheduling, an approach pioneered by Trietsch and others, and more recently extended in joint work by Baker and Trietsch. This book updates the coverage of ESS and adds coverage of safe scheduling as well as traditional stochastic scheduling. Because the new material comes from active researchers, the book surpasses competing texts in terms of its timeliness. And because the book retains the readability of its earlier versions, it should be the textbook of choice for instructors of scheduling courses. Finally, its title reinforces the experiences of two generations of students and scholars, providing a thread that establishes this volume, now in its second edition, as the latest update of a classic text.

New in the Second Edition

The second edition adds coverage of two major advances in stochastic scheduling and also addresses a few other new topics. One major development involves the application of branch and bound techniques and mathematical programming models to some safe scheduling problems. That new work, incorporated in Chapters 7 and 8 shows that the toolkit developed for deterministic scheduling can be applied to safe scheduling as well. The second major development builds on the validation of lognormal distributions for various empirical data sets. That new work implies that we can implement the full spectrum of analytics and modeling to scheduling, most importantly in project scheduling. Accordingly, Chapter 18 is a new chapter devoted to project analytics. The previous Chapter 18 is now Chapter 19, with an expanded coverage of hierarchical safe scheduling for projects. We also expanded Appendix A to include project analytics background material, including coverage of mixtures, which occur often, especially in projects. We also added a section on the lognormal tail distribution to Appendix B. Chapter 6 now includes a section on fuzzy scheduling and on robust scheduling. These approaches have been promoted as alternatives to stochastic scheduling that ostensibly avoid the need to fit stochastic distributions to observed processing times, but we argue that the distribution‐based approach remains the most useful one. That argument is especially valid now that stochastic scheduling models in general, and safe scheduling models in particular, can rely on validated distribution models.

Acknowledgments

We wish to acknowledge Lilit Mazmanyan of the American University of Armenia for her assistance with many detailed aspects of the first‐edition’s preparation. We also wish to acknowledge a set of first‐edition reviewers who provided guidance to our editors as well as anonymous comments and suggestions to us. This set includes Edwin Cheng (The Hong Kong Polytechnic University), Zhi‐Long Chen (University of Maryland), Chung‐Yee Lee (Hong Kong University of Science and Technology), Michael Magazine (University of Cincinnati), Stephen Powell (Dartmouth College), and Scott Webster (Syracuse University).