1. A computer-implemented method of training a classifier, such that the trained classifier is configured to map an instance to one of a plurality of classes, comprising: providing a data framework corresponding to a plurality of instances and a plurality of features, the data framework tangibly embodied in a computer-readable medium; providing a query space, wherein each of a plurality of queries of the query space comprises a subset of the plurality of instances, a subset of the plurality of features and a relevant characteristic function that describes, for that query, a function of instance-feature values associated with that query and of the instance-class probabilities associated with that query, wherein the instance-class probabilities are an indication of a probabilistic model of mapping of the instances associated with the query to at least one of the plurality of classes, the query space tangibly embodied in a computer-readable medium; operating a computing device to receive an indication of commentary from at least one editor for each of the plurality of queries of the query space, wherein the commentary for each query being the editor's estimate of the true value of the relevant characteristic for that query and storing the estimates in the query space in correspondence with the queries; maintaining a classifier framework tangibly embodied in a computer-readable medium, the classifier framework configured to provide class probabilities for the instances according to a tunable parameter vector; operating a computing device to determine, from the classifier model, relevant characteristic values corresponding to the queries in the query space; operating a computing device to determine a distortion value for each query by applying a distortion function to a deviation of the classifier framework response from the indication of editorial commentary for that query; and operating a computing device to adjust the tunable parameter vector based on a cost function that considers a regularization component and the distortion values over the plurality of queries for which the editors gave commentary.