Author name cluster

Viktor Schlegel

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6 papers

2 author rows

ICML Conference 2025 Conference Paper

BRIDGE: Bootstrapping Text to Control Time-Series Generation via Multi-Agent Iterative Optimization and Diffusion Modeling

Hao Li 0074
Yu-Hao Huang 0002
Chang Xu 0008
Viktor Schlegel
Renhe Jiang
Riza Batista-Navarro
Goran Nenadic
Jiang Bian 0002

Time-series Generation (TSG) is a prominent research area with broad applications in simulations, data augmentation, and counterfactual analysis. While existing methods have shown promise in unconditional single-domain TSG, real-world applications demand for cross-domain approaches capable of controlled generation tailored to domain-specific constraints and instance-level requirements. In this paper, we argue that text can provide semantic insights, domain information and instance-specific temporal patterns, to guide and improve TSG. We introduce “Text-Controlled TSG”, a task focused on generating realistic time series by incorporating textual descriptions. To address data scarcity in this setting, we propose a novel LLM-based Multi-Agent framework that synthesizes diverse, realistic text-to-TS datasets. Furthermore, we introduce Bridge, a hybrid text-controlled TSG framework that integrates semantic prototypes with text description for supporting domain-level guidance. This approach achieves state-of-the-art generation fidelity on 11 of 12 datasets, and improves controllability by up to 12% on MSE and 6% MAE compared to no text input generation, highlighting its potential for generating tailored time-series data.

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ECAI Conference 2025 Conference Paper

DocDiscNER: Enhanced Document-Level Discontinuous NER via Coordination Ellipses Resolution and Self-Consistency Decoding

Areej Alhassan
Viktor Schlegel
Rina Carines Cabral
Riza Batista-Navarro
Soyeon Caren Han
Josiah Poon
Goran Nenadic

Identifying entities in medical text often involves dealing with discontinuous word sequences or entities sharing a common head, which pose significant challenges for traditional Named Entity Recognition (NER) systems. Current state-of-the-art discontinuous NER models typically process each sentence in isolation, overlooking valuable intra-sentence context. However, recent studies have shown that large language models (LLMs) perform exceptionally well when provided such context. In this work, we introduce DocDiscNER, a novel approach to discontinuous NER, which features (i) a context-aware document chunking method that provides contextually related segments as input for LLM-based NER models; (ii) a dataset and approach for coordination ellipses resolution, to address candidate spans sharing common heads and (iii) a self-consistency decoding strategy that uses self-ensembling and a majority voting mechanism to select the most consistent predictions as entity spans. We demonstrate the effectiveness and generalisability of our method on three discontinuous NER benchmarks, achieving new state-of-the-art (SOTA) performance on two of them–CADEC and ShARe-14 (2. 48 and 2. 2 absolute F1 points gain, respectively); while achieving competitive results on ShARe-13. In addition, our method surpasses previous SOTA performance specifically in recognising discontinuous mentions. A deeper analysis unveils that incorporating semantically relevant context significantly enhances overall NER performance compared to using individual sentences as input.

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EAAI Journal 2025 Journal Article

Learning to generate and evaluate fact-checking explanations with transformers

Darius Feher
Abdullah Khered
Hao Zhang
Riza Batista-Navarro
Viktor Schlegel

In an era increasingly dominated by digital platforms, the spread of misinformation poses a significant challenge, highlighting the need for solutions capable of assessing information veracity. Our research contributes to the field of Explainable Artificial Antelligence (XAI) by developing transformer-based fact-checking models that contextualise and justify their decisions by generating human-accessible explanations. Importantly, we also develop models for automatic evaluation of explanations for fact-checking verdicts across different dimensions such as (self)-contradiction, hallucination, convincingness and overall quality. By introducing human-centred evaluation methods and developing specialised datasets, we emphasise the need for aligning Artificial Intelligence (AI)-generated explanations with human judgements. This approach not only advances theoretical knowledge in XAI but also holds practical implications by enhancing the transparency, reliability and users’ trust in AI-driven fact-checking systems. Furthermore, the development of our metric learning models is a first step towards potentially increasing efficiency and reducing reliance on extensive manual assessment. Based on experimental results, our best performing generative model achieved a Recall-Oriented Understudy for Gisting Evaluation-1 (ROUGE-1) score of 47. 77 demonstrating superior performance in generating fact-checking explanations, particularly when provided with high-quality evidence. Additionally, the best performing metric learning model showed a moderately strong correlation with human judgements on objective dimensions such as (self)-contradiction and hallucination, achieving a Matthews Correlation Coefficient (MCC) of around 0. 7.

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AAAI Conference 2025 Conference Paper

MEDSAGE: Enhancing Robustness of Medical Dialogue Summarization to ASR Errors with LLM-generated Synthetic Dialogues

Kuluhan Binici
Abhinav Ramesh Kashyap
Viktor Schlegel
Andy T. Liu
Vijay Prakash Dwivedi
Thanh-Tung Nguyen
Xiaoxue Gao
Nancy F. Chen

Automatic Speech Recognition (ASR) systems are pivotal in transcribing speech into text, yet the errors they introduce can significantly degrade the performance of downstream tasks like summarization. This issue is particularly pronounced in clinical dialogue summarization, a low-resource domain where supervised data for fine-tuning is scarce, necessitating the use of ASR models as black-box solutions. Employing conventional data augmentation for enhancing the noise robustness of summarization models is not feasible either due to the unavailability of sufficient medical dialogue audio recordings and corresponding ASR transcripts. To address this challenge, we propose MEDSAGE, an approach for generating synthetic samples for data augmentation using Large Language Models (LLMs). Specifically, we leverage the in-context learning capabilities of LLMs and instruct them to generate ASR-like errors based on a few available medical dialogue examples with audio recordings. Experimental results show that LLMs can effectively model ASR noise, and incorporating this noisy data into the training process significantly improves the robustness and accuracy of medical dialogue summarization systems. This approach addresses the challenges of noisy ASR outputs in critical applications, offering a robust solution to enhance the reliability of clinical dialogue summarization.

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NeurIPS Conference 2025 Conference Paper

MIRA: Medical Time Series Foundation Model for Real-World Health Data

Hao Li
Bowen Deng
Chang Xu
ZhiYuan Feng
Viktor Schlegel
Yu-Hao Huang
Yizheng Sun
Jingyuan Sun

A unified foundation model for medical time series—pretrained on open access and ethically reviewed medical corpora—offers the potential to reduce annotation burdens, minimize model customization, and enable robust transfer across clinical institutions, modalities, and tasks, particularly in data-scarce or privacy-constrained environments. However, existing time series foundation models struggle to handle medical time series data due to its inherent challenges, including irregular intervals, heterogeneous sampling rates, and frequent missingness. To address these challenges, we introduce MIRA, a unified foundation model specifically designed for medical time series forecasting. MIRA incorporates a Continuous-Time Rotary Positional Encoding that enables fine-grained modeling of variable time intervals, a frequency-specific mixture-of-experts layer that routes computation across latent frequency regimes to further promote temporal specialization, and a Continuous Dynamics Extrapolation Block based on Neural ODE that models the continuous trajectory of latent states, enabling accurate forecasting at arbitrary target timestamps. Pretrained on a large-scale and diverse medical corpus comprising over 454 billion time points collect from publicly available datasets, MIRA achieving reductions in forecasting errors by an average of 8% and 6% in out-of-distribution and in-distribution scenarios, respectively. We also introduce a comprehensive benchmark spanning multiple downstream clinical tasks, establishing a foundation for future research in medical time series modeling.

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AAAI Conference 2021 Conference Paper

Semantics Altering Modifications for Evaluating Comprehension in Machine Reading

Viktor Schlegel
Goran Nenadic
Riza Batista-Navarro

Advances in NLP have yielded impressive results for the task of machine reading comprehension (MRC), with approaches having been reported to achieve performance comparable to that of humans. In this paper, we investigate whether stateof-the-art MRC models are able to correctly process Semantics Altering Modifications (SAM): linguistically-motivated phenomena that alter the semantics of a sentence while preserving most of its lexical surface form. We present a method to automatically generate and align challenge sets featuring original and altered examples. We further propose a novel evaluation methodology to correctly assess the capability of MRC systems to process these examples independent of the data they were optimised on, by discounting for effects introduced by domain shift. In a large-scale empirical study, we apply the methodology in order to evaluate extractive MRC models with regard to their capability to correctly process SAM-enriched data. We comprehensively cover 12 different state-of-the-art neural architecture configurations and four training datasets and find that – despite their well-known remarkable performance – optimised models consistently struggle to correctly process semantically altered data.

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