  The CALICE collaboration has published a detailed study of hadronic
interactions using data recorded with the highly granular CALICE
silicon-tungsten electromagnetic calorimeter (Si-W ECAL). Approximately 350,000
selected negative pion events at energies between 2 and 10 GeV have been
studied. The predictions of several physics models available within the Geant4
simulation tool kit are compared to this data. A reasonable overall description
of the data is observed; the Monte Carlo predictions are within 20 % of the
data, and for many observables much closer. The largest quantitative
discrepancies are found in the longitudinal and transverse distributions of the
reconstructed energy. Based on the good control of the data set and general
observables, the next step is to achieve a deeper understanding of hadronic
interactions by studying the interaction zone and by reconstructing secondaries
that emerge from the hadronic interaction in the Si-W ECAL.
