1. A computer-implemented method comprising: obtaining a model representation of a predictive model, wherein the model representation is associated with a respective user and expresses a respective predictive model; and selecting a model implementation for the model representation, the model implementation comprising one or more computer programs operable to be executed on one or more computing devices, and the model implementation being selected for the corresponding model representation based on one or more system usage properties associated with the user associated with the corresponding model representation; and causing execution of the selected model implementation.