Selecting and Merging: Towards Adaptable and Scalable Named Entity
  Recognition with Large Language Models
Authors: name: Zhuojun Ding; name: Wei Wei; name: Chenghao Fan
Published: 2025-06-28 08:28:52

Abstract: Supervised fine-tuning (SFT) is widely used to align large language models
(LLMs) with information extraction (IE) tasks, such as named entity recognition
(NER). However, annotating such fine-grained labels and training
domain-specific models is costly. Existing works typically train a unified
model across multiple domains, but such approaches lack adaptation and
scalability since not all training data benefits target domains and scaling
trained models remains challenging. We propose the SaM framework, which
dynamically Selects and Merges expert models at inference time. Specifically,
for a target domain, we select domain-specific experts pre-trained on existing
domains based on (i) domain similarity to the target domain and (ii)
performance on sampled instances, respectively. The experts are then merged to
create task-specific models optimized for the target domain. By dynamically
merging experts beneficial to target domains, we improve generalization across
various domains without extra training. Additionally, experts can be added or
removed conveniently, leading to great scalability. Extensive experiments on
multiple benchmarks demonstrate our framework's effectiveness, which
outperforms the unified model by an average of 10%. We further provide insights
into potential improvements, practical experience, and extensions of our
framework.