1. An active learning system comprising: a representation module which generates a visual representation of a set of unlabeled elements, the representation showing the unlabeled elements as data points in a space and showing each of a plurality of classes as a class point in the space, each class point having an associated visual identifier, positions of the data points in the space being dependent on the uncertainty of a model regarding a classification of the respective unlabeled elements, a visual identifier of each of the data points being dependent on the visual identifier of at least one of the class points and the uncertainty of the model regarding the classification of the element; a graphical user interface which displays the representation to an annotator and enables the annotator to select one of the elements for labeling with a class label for one of the classes; and an updating module which receives class labels applied by the annotator and updates the model.