In the dependency tree of an event expression, which refers to a verb phrase or a clause here, the head word is a verb. It’s intuitive that the head verb is the predicate of an involved event. And the distribution of its arguments in dependency paths has some regularity. It’s suggested by the observation that we can always find the subject and object in direct dependents (level-2 nodes) of the head, or in the level-3 nodes. We summarize these strong regularities as unambiguous rules, examples of which are demonstrated in Table 1.