Disentangling Semantics and Syntax in Sentence Embeddings with Pre-trained Language Models
This addresses the need for more effective semantic sentence embeddings in NLP, particularly for tasks sensitive to syntactic noise, though it is incremental as it builds on existing pre-trained models and paraphrase methods.
The paper tackles the problem of entangled semantic and syntactic information in sentence embeddings from pre-trained language models by introducing ParaBART, which learns disentangled representations through syntax-guided paraphrasing, resulting in state-of-the-art performance on unsupervised semantic similarity tasks and improved robustness against syntactic variation.
Pre-trained language models have achieved huge success on a wide range of NLP tasks. However, contextual representations from pre-trained models contain entangled semantic and syntactic information, and therefore cannot be directly used to derive useful semantic sentence embeddings for some tasks. Paraphrase pairs offer an effective way of learning the distinction between semantics and syntax, as they naturally share semantics and often vary in syntax. In this work, we present ParaBART, a semantic sentence embedding model that learns to disentangle semantics and syntax in sentence embeddings obtained by pre-trained language models. ParaBART is trained to perform syntax-guided paraphrasing, based on a source sentence that shares semantics with the target paraphrase, and a parse tree that specifies the target syntax. In this way, ParaBART learns disentangled semantic and syntactic representations from their respective inputs with separate encoders. Experiments in English show that ParaBART outperforms state-of-the-art sentence embedding models on unsupervised semantic similarity tasks. Additionally, we show that our approach can effectively remove syntactic information from semantic sentence embeddings, leading to better robustness against syntactic variation on downstream semantic tasks.