Domain-independent simulations share the same characteristics as usual computer simulations, with the exception of being related to no particular referent or phenomenon. We first propose a model of the processes followed respectively by designers and end-users of a simulation, which reveals the conditions that make a simulation domain dependent (or not) from the perspective of each of these actors. We then present the successive, less and less domain-dependent, versions of a simulation we developed and tested in a university-level epistemology course intended for prospective teachers. Finally, we describe the main characteristics of the problem-solving processes we observed among these students, engaged in an open-ended learning activity based upon this simulation.