The third voting model is a boosting model (Freund and Schapire, 1997), since has consistently turned in very competitive scores on related tasks such as named entity classification (Carreras et al., 2002) .
an AdaBoost.MH model was used (Schapire and Singer, 2000), which is a multiclass generalization of the original boosting algorithm, with boosting on top of decision stump classifiers (i.e., decision trees of depth one).