This result suggests that using a reduced tag set yields a more informative performance estimation for some specific task because irrelevant tagging errors are not taken into account, but it does not necessarily lead to increased performance  Table 4: Cross-genre F 1 performance of the tagging models; main diagonal represents performance using 10-fold cross-validation for the relevant original tags.
when tackling a specific syntactic phenomenon, only a subset of signs and tags may be involved.