In the previous phase, co-occurrence pairs of event expressions are acquired from the web corpus. Next, we extract the events’ predicate-argument structures (i.e., “[Subj] [Pre] [Obj]” instances) relied on dependency syntactic structures of event expressions.
This idea is inspired by the event extraction work in (Zhao, 2008), which recognized eventarguments mainly based on the dependency-path feature employed in a maximum entropy classifier. Compared with the well-known phrase-structure, the dependency structure of a sentence is more likely to reflect the semantic relations between contiguous or noncontiguous words. And we further find that, the dependency structure can map to our event-argument structure in limited corpus, in spite of its weakness in generic semantic role labeling tasks (Xue, 2008). So, dependencies are used as the syntactic theory of choice.