Aleksis Ioannis Datseris


2025

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ExPe: Exact Positional Encodings for Generative Transformer Models with Extrapolating Capabilities
Aleksis Ioannis Datseris | Sylvia Vassileva | Ivan K. Koychev | Svetla Boytcheva
Proceedings of the 15th International Conference on Recent Advances in Natural Language Processing - Natural Language Processing in the Generative AI Era

This paper introduces a novel approach to position embeddings in transformer models, named “Exact Positional Embeddings” (ExPE). An absolute positional embedding method that can extrapolate to sequences of lengths longer than the ones it was trained on. Traditional transformer models rely on absolute or relative position embeddings to incorporate positional information into token embeddings, which often struggle with extrapolation to sequences longer than those seen during training. Our proposed method utilizes a novel embedding strategy that encodes exact positional information by overriding specific dimensions of the embedding vectors, thereby enabling a more precise representation of token positions. The proposed approach not only maintains the integrity of the original embeddings but also enhances the model’s ability to generalize to longer sequences. In causal language modeling, our ExPE embeddings significantly reduce perplexity compared to rotary and sinusoidal embeddings, when tested on sequences longer than those used in training. The code and supplementary materials can be found in

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End-to-End Deep Learning for Named Entity Recognition and Relation Extraction in Gut-Brain Axis PubMed Abstracts
Aleksis Ioannis Datseris | Mario Kuzmanov | Ivelina Nikolova-Koleva | Dimitar Taskov | Svetla Boytcheva
Proceedings of the 15th International Conference on Recent Advances in Natural Language Processing - Natural Language Processing in the Generative AI Era

This is a comparative study tackling named entity recognition and relation extraction from PubMed abstracts with focus on the gut-brain interplay. The proposed systems for named entity recognition cover a range of models and techniques from traditional gazetteer-based approaches, transformer-based approaches, transformer domain adaptation, large models pre-training as well as LLM prompting. The best performing model among these achieves 82.53% F1-score. The relation extraction task is addressed with ATLOP and LLMs and their best results reach F1 up to 63.80% on binary relation extraction, 89.40% on ternary tag-based relation extraction and 40.32% on ternary mention-based relation extraction.