This has a two-fold benefit: i) introduces a generalization level over surface forms; ii) provide to the parsing algorithm only the essential information, since POS tags are directly related to syntactic constituents and are sufficient to induce the syntactic structure of a sentence.
in our system, the role played by POS tags in syntactic parsing is played by entity components, annotated by CRF.for named entity annotation it is not true that components are sufficient to induce the entity tree.