8. A system, comprising: a data processing apparatus; and a memory storage apparatus in data communication with the data processing apparatus, the memory storage apparatus storing instructions executable by the data processing apparatus and that upon such execution cause the data processing apparatus to perform operations comprising: determining, by the data processing apparatus, a potential match candidate from among candidates ranked by predictors, each predictor respectively ranking the candidates according to likelihoods for matching an object as predicted by the respective predictor, and each predictor being different from each other predictor; identifying, for each predictor and by the data processing apparatus, a first value that specifies a likelihood of the potential match candidate for matching the object as predicted by the predictor; identifying, for each predictor and by the data processing apparatus, a second value that is proportional to the ranking of the potential match candidate as predicted by the predictor; determining, by the data processing apparatus, a class probability score for the potential match candidate using the first value for each predictor and the second value for each predictor, the class probability score representing a probability that the potential match candidate is a match to the object; determining, by the data processing apparatus, that the class probability score satisfies a threshold; and determining, by the data processing apparatus, that the potential match candidate matches the object in response to determining that the class probability score satisfies the threshold.
13. The system of claim 8 , wherein the instructions upon execution cause the data processing apparatus to perform further operations comprising training the predictors, each predictor being trained using a different number of training candidates.