1. A computer-implemented method comprising: receiving input data for a predictive model comprising values for categorical variables and one or more of binary variables and continuous variables, the predictive model characterizing a level of risk for a data transaction; associating one or more of the categorical variables with one of a plurality of keys, each key having corresponding coefficients for at least a subset of the binary variables and the continuous variables, the coefficients being dependent on a value for the key; generating a composite value based on values for each of at least a subset of the binary variables and the continuous variables as calculated using the corresponding coefficients for each key; and initiating scoring of the data transaction by the predictive model using the binary variables, the continuous variables, and the composite variables.