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Multi-Field Adaptive Retrieval (2410.20056v2)

Published 26 Oct 2024 in cs.IR and cs.CL

Abstract: Document retrieval for tasks such as search and retrieval-augmented generation typically involves datasets that are unstructured: free-form text without explicit internal structure in each document. However, documents can have a structured form, consisting of fields such as an article title, message body, or HTML header. To address this gap, we introduce Multi-Field Adaptive Retrieval (MFAR), a flexible framework that accommodates any number of and any type of document indices on structured data. Our framework consists of two main steps: (1) the decomposition of an existing document into fields, each indexed independently through dense and lexical methods, and (2) learning a model which adaptively predicts the importance of a field by conditioning on the document query, allowing on-the-fly weighting of the most likely field(s). We find that our approach allows for the optimized use of dense versus lexical representations across field types, significantly improves in document ranking over a number of existing retrievers, and achieves state-of-the-art performance for multi-field structured data.

Summary

  • The paper introduces an adaptive retrieval approach that dynamically predicts the importance of each document field by combining dense and lexical methods.
  • The methodology decomposes documents into individual fields with separate indexing, enhancing representation and retrieval accuracy compared to single-field models.
  • Experimental results on diverse datasets demonstrate that the hybrid approach outperforms traditional methods by effectively adapting to query-specific field relevance.

Multi-Field Adaptive Retrieval: A Technical Overview

The paper introduces the Multi-Field Adaptive Retrieval (mFAR) framework, which addresses the complexities involved in document retrieval from structured data sources. Unlike standard retrieval tasks that rely on unstructured data, mFAR is designed to handle documents with multiple fields, such as titles, timestamps, and content body. The framework leverages both dense and lexical methods, introducing a novel adaptive weighting mechanism that predicts the importance of different document fields based on the query.

Methodology

The mFAR framework consists of two major components:

  1. Field Decomposition and Indexing: Documents are decomposed into individual fields, and each field is indexed separately using both dense (vector-based) and lexical methods. This dual indexing facilitates richer representation and flexibility in retrieving relevant information.
  2. Adaptive Weighting Model: Unlike traditional retrieval systems that might treat a document as a monolithic entity, mFAR trains a model to predict the importance of each field dynamically. The relevance is assessed based on the query, allowing the system to assign weights to different fields and even choose between using dense or lexical scoring mechanisms for each field.

The authors employ a contrastive learning approach to fine-tune the neural model, optimizing it to differentiate between relevant and irrelevant documents across the various fields.

Experimental Validation

The experiments are conducted on diverse datasets from the STaRK collection, which includes structured data in domains such as product reviews (Amazon), academic articles (MAG), and biomedical knowledge (Prime). The researchers compare their method against state-of-the-art methods, including vector similarity search methods and LLM-based re-ranking baselines.

Key findings include:

  • Hybrid retrieval methods combining both dense and lexical scorers significantly outperform approaches relying solely on one type of scoring.
  • The inclusion of multi-field data allows for better performance than single-field representation, particularly when dense representations are employed across datasets.
  • The adaptive weighting mechanism enables query-specific field emphasis, which translates to more accurate retrieval performance.

Implications and Future Directions

The implications of this work extend to both theoretical and practical domains. Theoretically, it demonstrates that combining multiple indexing and scoring methods tailored to structured data can enhance retrieval quality. Practically, the ability to adapt dynamically to query complexities and document structures provides an advantage, especially for complex applications such as retrieval-augmented generation (RAG) in AI systems.

Future research could explore expanding the mFAR framework to incorporate other modalities such as visual or audio data. Additionally, the integration of more sophisticated scoring functions and exploring the limits of pre-trained models in this structured context might yield further improvements in retrieval performance.

Conclusion

The mFAR framework marks an advancement in the field of information retrieval, particularly for structured data. By intelligently leveraging document structure and employing a hybrid scoring technique, it offers a nuanced approach that aligns better with the real-world complexities of data. This work lays a foundation for developing more effective retrieval solutions that can serve as a pivotal component in broader AI applications.

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