However,both SCIRun and Paraview have significant limitations.First,there is no separation between the definition of a dataflow and its instances.In order to execute a given dataflow with different parameters, users need to set these parameters, manually through a GUI - not scaling to more than a faw visualizations. Second, modifications to parameters or to the definition of a dataflow are destructive.Despite their limitations,SCIRun and Paraview show the importance of combining visualization with PSEs.