Disentangling Semantics and Syntax in Sentence Embeddings with Pre-trained Language Models

TL;DR

This paper introduces ParaBART, a model that disentangles semantic and syntactic information in sentence embeddings using syntax-guided paraphrasing, improving semantic similarity tasks and robustness to syntactic variation.

Contribution

ParaBART is the first model to explicitly separate semantics and syntax in sentence embeddings using syntax-guided paraphrasing with pre-trained language models.

Findings

ParaBART outperforms state-of-the-art models on semantic similarity tasks.

It effectively removes syntactic information, enhancing robustness.

Disentangling improves semantic understanding in NLP applications.

Abstract

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.