Schwabe: An Introduction to Analytic Gaming

William Schwabe wrote an entry on gaming for the Encyclopedia of Operations Research and Management Science in 1994 that was also released as a RAND paper. Unfortunately, the entry/paper is not available online at this time. It's only 2 or 3 pages in the encyclopedia, and the RAND paper is only 7 pages long (double spaced), but it does a good job of laying out the basics of gaming as a policy research tool. It's a bit short to quote at length, but here are several points:

Few methods have been so inadequately named, prompting ridicule from skeptics and attempts by adherents to call it something more serious sounding or descriptive, such as "operational gaming," "simulation gaming," "free-form gaming," and, in defense analysis, "war gaming" and "political-military gaming."
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Unlike many other techniques of analysis, gaming is not a solution method. The output of a game is not a forecast, solution, or rigorous validation. The output of a good game is increased understanding.
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Gaming has often not been as well integrated into studies using other methodologies as might be warranted. Gaming is but one form of analysis to inform policy, managerial, or operational decisions.

In addition, Schwabe quotes Clark Abt's 1970 book, Serious Games, in his definition of a game in his first paragraph. It's a book I'll have to pick up at some point (and apparently it was just reprinted in paperback in 2002), but for now:

Clark Abt (1970) defines a game as "an activity among two or more independent decision-makers seeking to achieve their objectives in some limiting context."

Note the importance of multiple decision centers, just as Schelling noted (as mentioned previously here). Schwabe quoted some of the same portions of Schelling's section in Crisis Games 27 Years Later that I did in his description of what games can produce that other research methods cannot.

For a very basic look at gaming as a research tool, this is a remarkably successful 7 pages. I have the RAND report, not the encyclopedia entry, but I believe they are about the same. It wouldn't be worth the $18 RAND is charging for the paper, though, and it shows the importance of checking the page count before purchasing thinktank reports online. I got mine through interlibrary loan, and I expect that the encyclopedia is widely available at university libraries.