Annif System Blends Old and New AI for Top Subject Indexing

A new paper reveals how combining traditional AI with LLMs can significantly improve content categorization.

The Annif system, detailed in a new paper, achieved top rankings at SemEval-2025 by integrating traditional machine learning with large language models (LLMs). This hybrid approach significantly improves subject indexing for bibliographic records, especially in multilingual contexts. It highlights a powerful new direction for AI development.

August 25, 2025

4 min read

Annif System Blends Old and New AI for Top Subject Indexing

Key Facts

  • The Annif system participated in SemEval-2025 Task 5 (LLMs4Subjects).
  • Annif combined traditional NLP/ML techniques with LLM-based methods.
  • The system ranked 1st in the all-subjects category and 2nd in tib-core-subjects.
  • LLMs were used for translation and synthetic data generation.
  • The approach improved subject indexing accuracy and efficiency in multilingual contexts.

Why You Care

Ever struggled to find exactly what you’re looking for in a vast digital library or database? Imagine a system that can instantly and accurately categorize millions of documents, making information retrieval effortless. Do you ever wonder how search engines and digital libraries manage to organize so much information for you?

New research from the Annif system, presented at SemEval-2025, shows a way to do just that. They’ve combined older, AI methods with the latest large language models (LLMs) to create a highly effective subject indexing tool. This creation could dramatically change how you find and access information online.

What Actually Happened

The Annif system participated in SemEval-2025 Task 5, specifically focusing on ‘LLMs4Subjects,’ according to the announcement. This task challenged participants to create subject predictions for bibliographic records. These records came from the bilingual TIBKAT database, utilizing the GND subject vocabulary.

The Annif team’s approach was unique. They blended traditional natural language processing (NLP) and machine learning (ML) techniques. These methods were already implemented in the Annif set of tools. What’s more, they incorporated LLM-based methods. These LLMs were used for translation and generating synthetic data. They also helped merge predictions from different monolingual models, as detailed in the blog post.

This hybrid system performed exceptionally well. It ranked first in the all-subjects category. It also placed second in the tib-core-subjects category during quantitative evaluations. In qualitative evaluations, the system achieved a respectable fourth place, the study finds.

Why This Matters to You

This new approach has significant practical implications for you. Think about how much content you interact with daily. From academic papers to news articles, accurate categorization is crucial for discoverability. The Annif system’s success means better organization for vast amounts of data.

For example, imagine you are a researcher looking for specific articles on a niche topic. A system using Annif’s methods could provide far more precise search results. This saves you time and ensures you don’t miss vital information. It improves your ability to navigate complex information landscapes.

So, how might this blend of traditional AI and LLMs change the way you interact with digital content in the future? The team revealed that their findings “demonstrate the potential of combining traditional XMTC algorithms with modern LLM techniques to improve the accuracy and efficiency of subject indexing in multilingual contexts.”

Here’s a quick look at the Annif system’s performance:

CategoryRanking (Quantitative)Ranking (Qualitative)
All-subjects1st-
Tib-core-subjects2nd-
Overall (Qualitative)-4th

This shows a strong performance across different evaluation metrics.

The Surprising Finding

What’s truly surprising about the Annif system’s success is its hybrid nature. Many might assume that the latest LLMs would completely overshadow older AI techniques. However, the research shows that combining traditional XML Topic Maps (XMTC) algorithms with modern LLM methods yielded superior results.

Instead of a pure LLM approach, the Annif team augmented their existing set of tools. They used LLMs for specific tasks like translation and synthetic data generation. This strategic integration is what made the difference. It challenges the idea that newer system always replaces older methods entirely.

This finding suggests that the future of AI might not be about choosing one system over another. Instead, it could be about intelligently combining their strengths. It highlights the enduring value of established computational linguistics techniques. They still have a vital role to play alongside large language models.

What Happens Next

This successful demonstration points to a clear path forward for information management. We can expect to see more systems adopting this hybrid AI approach in the coming months. Libraries, archives, and large content platforms could implement similar strategies by late 2025 or early 2026.

For instance, a major online encyclopedia might use these techniques to improve its cross-language article linking. This would make it easier for users worldwide to access relevant information. Your favorite digital library could become even more intuitive and comprehensive.

For content creators and data managers, the actionable takeaway is clear. Explore how existing, AI tools can be enhanced with targeted LLM applications. Don’t discard methods in favor of entirely new ones. The industry implications are significant, suggesting a more nuanced evolution of AI systems. The paper states this approach can “improve the accuracy and efficiency of subject indexing in multilingual contexts.”