This approach is known to have three advantages: its applicability to many useful submodular objective functions, the efficiency of the greedy algorithm, and the provable performance guarantee.
, R K ⊆ V and function C e (S), which counts the number of times that n-gram e occurs in summary S ⊆ V , the ROUGE n score function is defined as We applied our method to compressive summarization tasks with the three kinds of objective functions: the coverage function, the one with rewards, and ROUGE 1 .