1. A training module, implementing by electronic computing functionality, for training a tagging model, comprising: logic configured to receive an explicitly-labeled training set, the explicitly-labeled training set including explicit labels that have been manually selected; logic configured to receive an implicitly-labeled training set, the implicitly-labeled training set including implicit labels that have been generated by a labeling system; and logic configured to train a tagging model based on the explicitly-labeled training set and the implicitly-labeled training set.