A feature targeting the context of a mention's head to model selectional preference.
the Berkeley System expands the feature space by feature conjunctions: If a pairwise feature f fires for current mention m c and antecedent mention m a , features f ∧ type(c) and f ∧ type(c) ∧ type(a) are also activated, where type(•) returns a mention type literal based on the head's POS.