Ontological Knowledge Learning for Relation Extraction

Publication Type:
Thesis
Issue Date:
2023
Full metadata record
The abundance of unstructured text online necessitates efficient Information Extraction (IE) methods. Relation Extraction (RE), a crucial IE sub-task, identifies relationships between entities, benefiting numerous Natural Language Processing (NLP) applications. RE, discerning entity relations in text, faces the demand of extensive training data. To address this, Distant Supervision (DS) is proposed but it leads to the wrong labelling problem and the long-tail relations. Previous works have employed Multi-Instance Learning (MIL) and selective attention networks for reducing noisy labelling, with extra ontological knowledge from Knowledge Graphs (KGs) enhancing entity pair understanding and leveraging relational hierarchies. We present progressive advancements in RE. It introduces a novel lightweight framework to better utilize ontological knowledge in texts. Building upon this, the research further innovates with a relation-augmented attention mechanism with effective hierarchical relation sharing for addressing the long-tail relations. Furthermore, the thesis employs specific prefix tuning with Pre-trained Language Models (PLMs) in limited data scenarios. This approach harnesses ontological knowledge, focusing on contrasting attributes between factual and counterfactual scenarios, significantly enhancing RE task performance.
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