1. A method of disambiguating a mention of an ambiguous entity, comprising: receiving a document that comprises the mention of the ambiguous entity; retrieving a set of candidate entities from an entity knowledge base based upon the mention of the ambiguous entity, wherein each of the candidate entities has a respective entity feature representation; generating a document feature representation based upon features of the document and the respective entity feature representations of the candidate entities; causing a processor to select a subset of features from the document feature representation based upon a measure of how discriminative the features from the document feature representation are for disambiguating the mention of the ambiguous entity; and determining a disambiguated result for the mention of the ambiguous entity based upon the subset of the features, wherein the disambiguated result is one of: an unknown entity; or one of the candidate entities.