Valeriu Vrabie
2026
Beyond Black-Box Labels: Interpretable Criteria for Diagnosing Subjective NLP Tasks
Nisrine Rair | Alban Goupil | Valeriu Vrabie | Emmanuel Chochoy
Findings of the Association for Computational Linguistics: ACL 2026
Nisrine Rair | Alban Goupil | Valeriu Vrabie | Emmanuel Chochoy
Findings of the Association for Computational Linguistics: ACL 2026
Subjective NLP datasets typically aggregate annotator judgments into a single gold label, making it difficult to diagnose whether disagreement reflects unclear criteria, collapsed distinctions, or legitimate plurality. We propose a schema-level diagnostic for auditing expert-designed annotation schemas prior to gold-label commitment, using only multi-annotator criterion judgments. The diagnostic separates two failure modes: unstable criteria with hard-to-operationalize boundaries, and systematic overlap that blurs the boundaries between mutually exclusive categories. Applied to persuasive value extraction in commercial documents, we find that disagreement is not diffuse: instability concentrates in a few criteria, while nearly half of covered sentences activate multiple categories. These signals align with where domain experts disagree, yielding an evidence-based audit for tightening guidelines, revising category structure, or reconsidering the annotation paradigm.
2025
When Annotators Disagree, Topology Explains: Mapper, a Topological Tool for Exploring Text Embedding Geometry and Ambiguity
Nisrine Rair | Alban Goupil | Valeriu Vrabie | Emmanuel Chochoy
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Nisrine Rair | Alban Goupil | Valeriu Vrabie | Emmanuel Chochoy
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Language models are often evaluated with scalar metrics like accuracy, but such measures fail to capture how models internally represent ambiguity, especially when human annotators disagree. We propose a topological perspective to analyze how fine-tuned models encode ambiguity and more generally instances.Applied to RoBERTa-Large on the MD-Offense dataset, Mapper, a tool from topological data analysis, reveals that fine-tuning restructures embedding space into modular, non-convex regions aligned with model predictions, even for highly ambiguous cases. Over 98% of connected components exhibit ≥ 90% prediction purity, yet alignment with ground-truth labels drops in ambiguous data, surfacing a hidden tension between structural confidence and label uncertainty.Unlike traditional tool such as PCA or UMAP, Mapper captures this geometry directly uncovering decision regions, boundary collapses, and overconfident clusters. Our findings position Mapper as a powerful diagnostic tool for understanding how models resolve ambiguity. Beyond visualization, it also enables topological metrics that may inform proactive modeling strategies in subjective NLP tasks.