Simulating biology: towards understanding what the simulation shows

When building simulations of complex systems the task of validation is often overlooked. Validation helps provide confidence in the simulation by exploring the link between the models that we build and the real complex system. We investigate software engineering validation techniques from outside the area of complex systems to assess their applicability for the types of simulation we build. We then provide an example of how such techniques can be applied to a complex systems simulation of cells migrating from blood vessels into lymph nodes through the walls of the blood vessels. We suggest that explicitly stating the modelling and simulation assumptions we make is key to the process of validation. Concluding, we highlight a possible process for validating complex systems that explicitly incorporates environmental aspects.