1. A method of processing data, the data comprising: a set of one or more system inputs; and a set of one or more system outputs; wherein each system output corresponds to a respective system input; each system input includes a plurality of data points, a first data point in the plurality and a second data point in the plurality being from a same raw data source ( 8 , 10 , 12 ), and the first data point being pre-processed using a pre-processing method different from a pre-processing method used to pre-process the second data point, the method comprising: for each of the first and second data points, inferring a value indicative of a significance of the pre-processing method used to pre-process that data point; wherein the step of inferring includes performing a machine learning algorithm on a given system input from the data and a further system input.