However, this model is not appropriate for the OntoNotes-4.0 data set, in which (in contrast to the ACE 2004 corpus) singleton mentions are not annotated: a specific noun phrase (NP) may correspond to a mention in one document but will not be a mention in another document.
we designed a high recall (∼ 90%) and low precision (∼ 35%) rule-based mention detection system that includes all phrases recognized as Named Entities (NE's) and all phrases tagged as NPs in the syntactic parse of the text.