Using content-level structures for summarizing microblog repost trees

A microblog repost tree provides strong clues on how an event described therein develops. To help social media users capture the main clues of events on mi-croblogging sites, we propose a novel re-post tree summarization framework by ef-fectively differentiating two kinds of mes-sages on repost trees called leaders and followers, which are derived from content-level structure information, i.e., contents of messages and the reposting relations. To this end, Conditional Random Fields (CRF) model is used to detect leaders across repost tree paths. We then present a variant of random-walk-based summariza-tion model to rank and select salient mes-sages based on the result of leader detec-tion. To reduce the error propagation cas-caded from leader detection, we improve the framework by enhancing the random walk with adjustment steps for sampling from leader probabilities given all the re-posting messages. For evaluation, we construct two annotated corpora, one for leader detection, and the other for repost tree summarization. Experimental results confirm the effectiveness of our method.