INFORMS Expository Writing Award

It is with great pleasure that the INFORMS Committee for the Expository Writing Award names Professor Ward Whitt of Columbia University as the recipient of its 2011 award. Ward Whitt is renowned for the many theoretical and applied results he has developed over 40+ years. As the author or coauthor of more than 325 journal articles in addition to his book Stochastic-Process Limits (Springer, 2002), Ward Whitt is a master expositor. His writing is exceptionally clear, and consequently he has succeeded in communicating his many findings to a large audience.

Examples of Professor Whitt’s expository skill are found in two of his early papers, “Approximating a Point Process by a Renewal Process” (Operations Research, 1982) and “The Queueing Network Analyzer” (Bell System Technical Journal, 1983). The first of this pair develops the theory underlying approximations for point processes that can be used to describe non-Markovian traffic in queueing networks or multiechelon inventory systems, while the second reports a software tool employing these approximations to analyze queueing networks with complicated topologies that allow customer traffic to merge, split or feed back as it flows through the system. These papers have each been cited hundreds of times, illustrating their import to the development of the literature in this area.

Ward Whitt’s search for practical tools with rigorous foundation is further demonstrated in his paper with Shlomo Halfin titled “Heavy-Traffic Limits for Queues with Many Exponential Servers” (Operations Research, 1981). Also heavily cited, this article established a new heavy traffic limit with a delay probability less than 1; the resulting Halfin-Whitt regime (often referred to as the QED or quality-and-efficiency-driven regime) now features regularly in analyses of many-server call centers and other service networks. Professor Whitt’s career-long interest in developing practical results for difficult queueing problems continues to the present day; indeed one of his most recent papers, “A Network of Time-Varying Many-Server Fluid Queues with Customer Abandonment (Operations Research, 2011, coauthored with Yunan Liu) testifies further to his clear and careful writing on these topics.

Professor Whitt’s expository output is even more impressive when one considers the journals in which he writes. Research reported by Ward Whitt and his coauthors appears regularly in the very best journals in operations research and stochastic processes including Operations Research, Management Science, Mathematics of Operations Research, Journal of Applied Probability, Advances in Applied Probability, Queueing Systems, and other leading outlets. In addition to his many scientific papers, Ward Whitt’s book Stochastic-Process Limits is a 600+ page treatise that brings together Donsker’s functional central limit theorem with queueing processes to create heavy-traffic stochastic-process limits for queues. These limits have the advantage of revealing key relationships and performance details that are often obscured when attempting to model such queues directly. The book is written so that readers with differing backgrounds in probability theory can learn at appropriate levels of technical expertise.

Professor Whitt’s writing is both clever and clear, and much of his material is indeed beautiful. For more than 40 years he has been hugely influential in propelling stochastic operations research forward in both theory and application. For these reasons, the Expository Writing Committee (Warren B. Powell, Richard Steinberg and Edward H. Kaplan) is pleased to name Ward Whitt as the recipient of the 2011 INFORMS Expository Writing Award.