In order to support realistic real-world processes, workflow systems need to be able to adapt to changes. Detecting the need to change and deciding what changes to carry out are very difficult. Simulation analysis can play an important role in this. It can be used in tuning quality of service metrics and in exploring "what-if" questions. Before a change is actually made, its possible effects can be explored with simulation. To facilitate rapid feedback, the workflow system (METEOR) and simulation system (JSIM) need to inter operate.In particular, workflow specification documents need to be translated into simulation model specification documents so that the new model can be executed/animated on-the-fly. Fortunately, modern Web technology (e.g., XML, DTD, XSLT) make this relatively straightforward. The utility of using simulation in adapting a workflow is illustrated with an example from a genome workflow.