Supervised Contrastive Learning for Interpretable Long Document Comparison

Recent advancements in deep learning techniques have transformed the area of semantic text matching. However, most of the state-of-the-art models are designed to operate with short documents such as tweets, user reviews, comments, etc., and have fundamental limitations when applied to long-form documents such as scientific papers, legal documents, and patents. When handling such long documents, there are three primary challenges: (i) The presence of different contexts for the same word throughout the document, (ii) Small sections of contextually similar text between two documents, but dissimilar text in the remaining parts -- this defies the basic understanding of "similarity", and (iii) The coarse nature of a single global similarity measure which fails to capture the heterogeneity of the document content. In this paper, we describe CoLDE: Contrastive Long Document Encoder -- a transformer-based framework that addresses these challenges and allows for interpretable comparisons of long documents. CoLDE uses unique positional embeddings and a multi-headed chunkwise attention layer in conjunction with a contrastive learning framework to capture similarity at three different levels: (i) high-level similarity scores between a pair of documents, (ii) similarity scores between different sections within and across documents, and (iii) similarity scores between different chunks in the same document and also other documents. These fine-grained similarity scores aid in better interpretability. We evaluate CoLDE on three long document datasets namely, ACL Anthology publications, Wikipedia articles, and USPTO patents. Besides outperforming the state-of-the-art methods on the document comparison task, CoLDE also proves interpretable and robust to changes in document length and text perturbations.