2 NEGRA's original annotation is as dependency trees with phrasal nodes, crossing branches, and no empty elements.
9,10 Note that this evaluation metric does not require correct attachment of the empty category into 8 A complete description of feature templates can be found at http://nlp.stanford.edu/˜rog/acl2004/templates/index.html 9 For purposes of comparability with Johnson (2002) we used Charniak's 2000 parser as P .