Explainable Semantic Textual Similarity via Dissimilar Span Detection

Fuente: arXiv
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Autores principales: Lozano, Diego Miguel, Dementieva, Daryna, Fraser, Alexander
Formato: Preprint
Publicado: 2026
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author Lozano, Diego Miguel
Dementieva, Daryna
Fraser, Alexander
author_facet Lozano, Diego Miguel
Dementieva, Daryna
Fraser, Alexander
contents Semantic Textual Similarity (STS) is a crucial component of many Natural Language Processing (NLP) applications. However, existing approaches typically reduce semantic nuances to a single score, limiting interpretability. To address this, we introduce the task of Dissimilar Span Detection (DSD), which aims to identify semantically differing spans between pairs of texts. This can help users understand which particular words or tokens negatively affect the similarity score, or be used to improve performance in STS-dependent downstream tasks. Furthermore, we release a new dataset suitable for the task, the Span Similarity Dataset (SSD), developed through a semi-automated pipeline combining large language models (LLMs) with human verification. We propose and evaluate different baseline methods for DSD, both unsupervised, based on LIME, SHAP, LLMs, and our own method, as well as an additional supervised approach. While LLMs and supervised models achieve the highest performance, overall results remain low, highlighting the complexity of the task. Finally, we set up an additional experiment that shows how DSD can lead to increased performance in the specific task of paraphrase detection.
format Preprint
id arxiv_https___arxiv_org_abs_2603_21174
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Explainable Semantic Textual Similarity via Dissimilar Span Detection
Lozano, Diego Miguel
Dementieva, Daryna
Fraser, Alexander
Computation and Language
Semantic Textual Similarity (STS) is a crucial component of many Natural Language Processing (NLP) applications. However, existing approaches typically reduce semantic nuances to a single score, limiting interpretability. To address this, we introduce the task of Dissimilar Span Detection (DSD), which aims to identify semantically differing spans between pairs of texts. This can help users understand which particular words or tokens negatively affect the similarity score, or be used to improve performance in STS-dependent downstream tasks. Furthermore, we release a new dataset suitable for the task, the Span Similarity Dataset (SSD), developed through a semi-automated pipeline combining large language models (LLMs) with human verification. We propose and evaluate different baseline methods for DSD, both unsupervised, based on LIME, SHAP, LLMs, and our own method, as well as an additional supervised approach. While LLMs and supervised models achieve the highest performance, overall results remain low, highlighting the complexity of the task. Finally, we set up an additional experiment that shows how DSD can lead to increased performance in the specific task of paraphrase detection.
title Explainable Semantic Textual Similarity via Dissimilar Span Detection
topic Computation and Language
url https://arxiv.org/abs/2603.21174