Monday, April 27, 2009


Brill, D. (1979) "The Use of Optimization Models in Public Sector Planning" Management Science 25(5):413-422

Coming full circle. Brill's paper offers an analysis on the role of modeling in public sector decision making. In much the same vein as Liebman's "Wicked Problem" paper from early in the series, Brill examines the role of optimization and simulation models in the decision making process. Brill examines the current (at the time) literature for examples of optimization models being used as a part of the decision support structure for public projects. Based on these examples he further develops the idea that optimization modeling has moved from being "the way" to "the answer" to being just another tool in the decision making kit. He even refers to the Liebman's analysis of "wicked" public problems to support his position on the role for modeling.
Overall this paper made a nice bookend for the semester literature series. Although I don't really think that Brill moved beyond the ideas put forward by Liebman his examples helped to further round out the concept. The evolution of use of modeling, both simulation and optimization, from problem sovlers to tools for finding possible solutions and developing alternatives is well established between the papers. (Yeah, I'm not really sure what that sentence was supposed to mean, but it sounded good at first) On a completely separate note, I was impressed by Brill's discussion of the need to consider solutions off the Pareto-front and the problem of developing a model in the absence of complete data. The idea that as new dimensions are added to the problem the new optimal solution will be sub-optimal in the earlier dimensions seems like an obvious concept but I had never really thought about before.

And because its the end of the semester... here's number two for the week (no pun intended).

Pan, T., Kao, J. (2009) "GA-QP Model to Optimize Sewer Design"
Kao and Pan employ a joint genetic algorithm/quadratic programming model to explore the design specifications for a municipal wastewater design. Building on the idea of "modeling to generate alternative" (taken from a paper written by Brill in 1982. Go Brill, Go) Pan and Kao use the coupled model system to create generate (genetic algorithm) and test (quadratic program) design alternative to arrive at a series of possible solutions. Although the coupled model system is able to produce multiple designs that satisfy the constraints, the authors point out early in their report that there are still several, mostly socio-political, issues that defy quantization and cannot be considered in the model. This returns us to a re-occurring theme of modeling as a tool to produce possible solutions but not "the answer". The issues that could not be included in the model are things that, in general, are best left up the decision makers anyway (dealing with neighborhoods and NIMBY, public sentiment, etc).