Match-Ignition: Plugging PageRank into Transformer for Long-form Text Matching

Semantic text matching models have been widely used in community question answering, information retrieval, and dialogue. However, these models cannot well address the long-form text matching problem. That is because there are usually many noises in the setting of long-form text matching, and it is difficult for existing semantic text matching to capture the key matching signals from this noisy information. Besides, these models are computationally expensive because they simply use all textual data indiscriminately in the matching process. To tackle the effectiveness and efficiency problem, we propose a novel hierarchical noise filtering model in this paper, namely Match-Ignition. The basic idea is to plug the well-known PageRank algorithm into the Transformer, to identify and filter both sentence and word level noisy information in the matching process. Noisy sentences are usually easy to detect because the sentence is the basic unit of a long-form text, so we directly use PageRank to filter such information, based on a sentence similarity graph. While words need to rely on their contexts to express concrete meanings, so we propose to jointly learn the filtering process and the matching process, to reflect the contextual dependencies between words. Specifically, a word graph is first built based on the attention scores in each self-attention block of Transformer, and keywords are then selected by applying PageRank on this graph. In this way, noisy words will be filtered out layer by layer in the matching process. Experimental results show that Match-Ignition outperforms both traditional text matching models for short text and recent long-form text matching models. We also conduct detailed analysis to show that Match-Ignition can efficiently capture important sentences or words, which are helpful for long-form text matching.