It is worth mentioning that the KBP Event Nugget Detection and Coreference task, which started in 2015, aims to address a major weakness of the ACE 2005 event coreference task.
aCE 2005 adopts a strict notion of event identity, with which two event mentions were annotated as coreferent if and only if "they had the same agent(s), patient(s), time, and location" (Song et al., 2015), and their event attributes (polarity, modality, genericity, and tense) were not incompatible.