Keyphrase generation (KG) aims to generate a set of summarizing words or phrases given a source document, while keyphrase extraction (KE) aims to identify them from the text. Because the search space is much smaller in KE, it is often combined with KG to predict keyphrases that may or may not exist in the corresponding document. However, current unified approaches adopt sequence labeling and maximization-based generation that primarily operate at a token level, falling short in observing and scoring keyphrases as a whole. In this work, we propose SIMCKP, a simple contrastive learning framework that consists of two stages: 1) An extractor-generator that extracts keyphrases by learning context-aware phraselevel representations in a contrastive manner while also generating keyphrases that do not appear in the document; 2) A reranker that adapts scores for each generated phrase by likewise aligning their representations with the corresponding document. Experimental results on multiple benchmark datasets demonstrate the effectiveness of our proposed approach, which outperforms the state-of-the-art models by a significant margin.
IntroductionKeyphrase prediction (KP) is a task of identifying a set of relevant words or phrases that capture the main ideas or topics discussed in a given document. Prior studies have defined keyphrases that appear in the document as present keyphrases and the opposites as absent keyphrases. High-quality keyphrases are beneficial for various applications such as information retrieval (Kim et al., 2013), text summarization (Pasunuru and Bansal, 2018), and translation (Tang et al., 2016). KP methods are generally divided into keyphrase extraction (KE) (Witten * Work done during an internship at Naver Webtoon.