An ontology-guided, language model-assisted approach for theme-specific information extraction

Xiao, Jinfeng

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https://hdl.handle.net/2142/129450 Copy

Description

Title

An ontology-guided, language model-assisted approach for theme-specific information extraction

Author(s)

Xiao, Jinfeng

Issue Date

2025-04-25

Director of Research (if dissertation) or Advisor (if thesis)

Han, Jiawei

Doctoral Committee Chair(s)

Han, Jiawei

Committee Member(s)

• Zhai, ChengXiang
• Ji, Heng
• Elkaref, Mohab

Department of Study

Computer Science

Discipline

Computer Science

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Large language models
• Information extraction
• Information retrieval
• Ontology
• Taxonomy

Abstract

In an era of information explosion, text data are generated every second so fast that digesting raw texts becomes increasingly time-consuming. The research field of text mining aims at automatically extracting structured knowledge from massive unstructured text data. An essential step in the process of converting text to knowledge is information extraction (IE), which aims at extracting information about entities and relations from text. In recent years, the development of large language models (LLMs) has shed light on new possibilities of performing better IE under label-sparse settings that are hard, if not impossible, for traditional methods due to the lack of human supervision that is necessary for model training. On the other hand, LLM-assisted domain-specific IE applications often face long-tail challenges, which refer to suboptimal performance due to the fact that many important signals (e.g., entities and relations) in the target domain are sparse in the pre-training corpora and are thus not handled well by pre-trained LLMs. Such long-tail problems become more severe when we move one step further from domains into highly specialized themes. My dissertation research explores the utilization of theme-specific entity type ontologies to improve the long-tail robustness of LLMs for IE tasks. I utilize such ontologies to 1) retrieve theme-relevant documents from large corpora based on the distribution of query entities and relations on the ontology, 2) find entities from large corpora that have fine-grained entity types relevant to the query entities, 3) retrieve relevant external, non-parametric knowledge in a structured manner to augment LLM queries, and 4) organize the internal, parametric knowledge of LLMs into relation structures for robust open relation extraction. While the 1st and 3rd components focus more on information retrieval (IR), all the components together form an end-to-end framework for corpus-level theme-specific IE. Extensive experiments demonstrate that my solutions achieve state-of-the-art performance with remarkable long-tail robustness. One more notable advantage of my approach is that it works purely at the LLM inference stage. No extra pre-training or post-training is required. This means my approach works without additional annotation efforts or heavy resource consumption. All my methods are easy to deploy on a single graphics processing unit (GPU) with any recent LLMs, and thus, my solutions are highly accessible to ordinary people. In addition, my design essentially separates data from models, which ensures there is technically zero risk of leaking private user data. Thus, my approach is highly suitable for sensitive domain applications such as medical care and legal advising.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129450

Copyright and License Information

Copyright 2025 Jinfeng Xiao

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