(=> (Pn-Arrow ?Self) (And (Exists (?A) (And (Part-Of ?Self ?A) (Petri-Net ?A))) (Exists (?B) (And (Represents ?Self ?B) (Time-Span ?B) (Exists (?C) (And (Precedes ?B ?C) (*Phase ?C))) (Forall (?C ?D) (=> (And (Precedes ?B ?C) (Precedes ?B ?D)) (= ?C ?D)))))))