Improving the flexibility of simulation modeling with aspects.

While simulation and modeling serve as increasingly popular tools in addressing complex policy challenges, modeling projects are often encumbered by significant complexity within the model itself. This includes complexity extending from software engineering challenges, implementation, management of the model execution, difficulty in maintaining metadata to cross-link models, scenario results, associated simulation results, and a dependence of knowledge-users on modelers to modify model output and visualization mechanisms to explore patterns of interest. Furthermore, debugging of and developing confidence in a model often requires enabling/disabling tracing output of various model quantities. We present techniques to enhance flexibility, transparency, usefulness and effectiveness of simulation modeling by using Aspect-Oriented Programming to automatically manage the high-level execution results (Run Log) and, separately, low-level details (Trace Log) associated with model executions. With an eye towards enabling scenario reproducibility, Run Log documents the scenarios run for a given model, and records the associated model version, scenario assumptions and elements of output. The Aspect framework for Trace Log eliminates boilerplate logging code within models, supports flexibly enabling/disabling logging, improves the robustness of the model by providing easy mechanisms of debugging, and supports knowledge-users in exploring model output. We describe the framework, experiments conducted, and feedback received.