Sigmalaw PBSA-A Deep Learning Model for Aspect-Based Sentiment Analysis for the Legal Domain

I. Rajapaksha, C. Mudalige, D. Karunarathna, N. Silva, A. Perera, and G. Ratnayaka International Conference on Database and Expert Systems Applications, Springer, 2021, pp. 125--137, Legal information retrieval holds a significant importance to lawyers and legal professionals. Its significance has grown as a result of the vast and rapidly increasing amount of legal documents available via electronic means. Legal documents, which can be considered flat file databases, contain information that can be used in a variety of ways, including arguments, counter-arguments, justifications, and evidence. As a result, developing automated mechanisms for extracting important information from legal opinion texts can be regarded as an important step toward introducing artificial intelligence into the legal domain. Identifying advantageous or disadvantageous statements within these texts in relation to legal parties can be considered as a critical and time consuming task. This task is further complicated by the relevance of context in automatic legal information extraction. In this paper, we introduce a solution to predict sentiment value of sentences in legal documents in relation to its legal parties. The Proposed approach employs a fine-grained sentiment analysis (Aspect-Based Sentiment Analysis) technique to achieve this task. Sigmalaw PBSA is a novel deep learning-based model for ABSA which is specifically designed for legal opinion texts. We evaluate the Sigmalaw PBSA model and existing ABSA models on the SigmaLaw-ABSA dataset which consists of 2000 legal opinion texts fetched from a public online data base. Experiments show that our model outperforms the state-of-the-art models. We also conduct an ablation study to identify which methods are most effective for legal texts.