1. A method, comprising: receiving a plurality of training inputs, each training input comprising at least one training feature and at least one training class label identifying a training class; receiving a plurality of training outputs, each training output corresponding to a training input, each training output comprising a training membership value that indicates the membership status of an entity corresponding to the training input with respect to the training class; and training a machine learning system based on the training inputs and the training outputs to obtain a trained machine learning system.