Summarizing a Document by Trimming a Nested Tree Structure

Abstract

Many methods of text summarization that have recently been proposed combine sentence selection and sentence compression. Although the dependency between words has been used in most of these methods, the dependency between sentences, i.e., the rhetorical structure, has not been exploited in such joint methods. We use both the dependency between words and the dependency between sentences by constructing a nested tree, in which nodes in a document tree representing the dependency between sentences were replaced by a sentence tree representing the dependency between words. We formulate a summarization task as a combinatorial optimization problem, in which the nested tree is trimmed without losing important content in the source document. The results from an empirical evaluation revealed that our method based on the trimming of the nested tree significantly improved the performance of text summarization.