Iacopo Ghinassi


2024

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Language Pivoting from Parallel Corpora for Word Sense Disambiguation of Historical Languages: A Case Study on Latin
Iacopo Ghinassi | Simone Tedeschi | Paola Marongiu | Roberto Navigli | Barbara McGillivray
Proceedings of the 2024 Joint International Conference on Computational Linguistics, Language Resources and Evaluation (LREC-COLING 2024)

Word Sense Disambiguation (WSD) is an important task in NLP, which serves the purpose of automatically disambiguating a polysemous word with its most likely sense in context. Recent studies have advanced the state of the art in this task, but most of the work has been carried out on contemporary English or other modern languages, leaving challenges posed by low-resource languages and diachronic change open. Although the problem with low-resource languages has recently been mitigated by using existing multilingual resources to propagate otherwise expensive annotations from English to other languages, such techniques have hitherto not been applied to historical languages such as Latin. In this work, we make the following two major contributions. First, we test such a strategy on a historical language and propose a new approach in this framework which makes use of existing bilingual corpora instead of native English datasets. Second, we fine-tune a Latin WSD model on the data produced and achieve state-of-the-art results on a standard benchmark for the task. Finally, we release the dataset generated with our approach, which is the largest dataset for Latin WSD to date. This work opens the door to further research, as our approach can be used for different historical and, generally, under-resourced languages.

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When Cohesion Lies in the Embedding Space: Embedding-Based Reference-Free Metrics for Topic Segmentation
Iacopo Ghinassi | Lin Wang | Chris Newell | Matthew Purver
Proceedings of the 2024 Joint International Conference on Computational Linguistics, Language Resources and Evaluation (LREC-COLING 2024)

In this paper we propose a new framework and new methods for the reference-free evaluation of topic segmentation systems directly in the embedding space. Specifically, we define a common framework for reference-free, embedding-based topic segmentation metrics, and show how this applies to an existing metric. We then define new metrics, based on a previously defined cohesion score, Average Relative Proximity. Using this approach, we show that Large Language Models (LLMs) yield features that, if used correctly, can strongly correlate with traditional topic segmentation metrics based on costly and rare human annotations, while outperforming existing reference-free metrics borrowed from clustering evaluation in most domains. We then show that smaller language models specifically fine-tuned for different sentence-level tasks can outperform LLMs several orders of magnitude larger. Via a thorough comparison of our metric’s performance across different datasets, we see that conversational data present the biggest challenge in this framework. Finally, we analyse the behaviour of our metrics in specific error cases, such as those of under-generation and moving of ground truth topic boundaries, and show that our metrics behave more consistently than other reference-free methods.

2023

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Lessons Learnt from Linear Text Segmentation: a Fair Comparison of Architectural and Sentence Encoding Strategies for Successful Segmentation
Iacopo Ghinassi | Lin Wang | Chris Newell | Matthew Purver
Proceedings of the 14th International Conference on Recent Advances in Natural Language Processing

Recent works on linear text segmentation have shown new state-of-the-art results nearly every year. Most times, however, these recent advances include a variety of different elements which makes it difficult to evaluate which individual components of the proposed methods bring about improvements for the task and, more generally, what actually works for linear text segmentation. Moreover, evaluating text segmentation is notoriously difficult and the use of a metric such as Pk, which is widely used in existing literature, presents specific problems that complicates a fair comparison between segmentation models. In this work, then, we draw from a number of existing works to assess which is the state-of-the-art in linear text segmentation, investigating what architectures and features work best for the task. For doing so, we present three models representative of a variety of approaches, we compare them to existing methods and we inspect elements composing them, so as to give a more complete picture of which technique is more successful and why that might be the case. At the same time, we highlight a specific feature of Pk which can bias the results and we report our results using different settings, so as to give future literature a more comprehensive set of baseline results for future developments. We then hope that this work can serve as a solid foundation to foster research in the area, overcoming task-specific difficulties such as evaluation setting and providing new state-of-the-art results.