A complex system has many variables which interact with each other. Engineering software is one technology which can assist how different technology can perform under different conditions (e.g. weather or resisting corrosion).
An example is how an airplane will perform under different weather environments. Since airplanes are very complex, they can focus on one area such as the wings and model how they can perform against conditions (e.g. high winds, torrential rain, or snow). By focusing on one area to test, they can make better predictions for this model.