Márcio Barros Cláudia Werner Guilherme Travassos Explaining the Behavior of System Dynamics Models POSTER OBJECTIVE To present a technique that helps the analysis of system dynamics models COPPEUFRJ

n EVENT TRACING Ü Maps simulation trends overtime to events Ü Uses state machines whose behavior can be traced to changes suffered by variables in a SD model Ü Changes trigger messages, which are shown to the analyst, helping to understand model behavior  A state represents a set of properties found in the model in a simulation step Ü A transition has an associated condition, which depends on a model variable, and a message, sent to the user when the transition fires Ü In a simulation step, the transitions from the current state are evaluated

n Example: Software project SD model Ü Developers work to accomplish tasks Ü When the project is late, developers start overworking Ü Later, developers return to normal work rate n Implications: "de Marco’s Law" Ü "While overworking, developers work more, not better” Ü Error generation rates may grow ! Hours <= 8 Hours > 8 Normal Work Rate Overwork

Step $Step: Developers started overworking Step $Step: Developers started overworking </STATE> Step $Step: Developers relaxed Step $Step: Developers relaxed </STATE></EVENTSET>