Physically-based numerical modeling of the cosmic-ray processes is the most fundamental method of evaluating the systematics of cosmogenic production. Such models are the best basis for comparison for all the kinds of data described in this proposal. They should provide an excellent means of calculating the effects of complex past variations of conditions (e.g., correcting short-term data for the effect of the solar-cycle, glacial/interglacial changes in atmospheric pressure or variations in the non-dipole geomagnetic field). Feedback between the modeling effort and the experimental campaign should contribute to both. Convergence between the results of these approaches will be an important test for the project.