A key feature of Vensim is the ability to do multiple simulations on a model under different conditions to test the impact that changes in constants (or lookups) have on model behavior. Vensim also stores all the data for all variables for each simulation run, so that you can easily access information about the behavior of any variable in any run. Experiments are performed by temporarily changing Constant or Lookup values and then simulating the model. This way, your underlying model stays the same, an unchanging reference point.
