Conventionally, when measuring the quality of a system for an information extraction task, a predicted entity is counted as correct if it exactly matches the boundaries of a corresponding entity in the gold standard; there is thus no reward for close matches.
since the boundaries of the spans annotated in the MPQA corpus are not strictly defined in the annotation guidelines , measuring precision and recall using exact boundary scoring will result in figures that are too low to be indicative of the usefulness of the system.