Storyline Trees: Hierarchical Representations for Long-Form Narratives

Litu Ou, Mirella Lapata


Abstract
Long-form narratives are challenging for long-context models because their structure is implicit: events, characters, and plotlines interact across hundreds of pages without the explicit cues that guide navigation in structured documents. We address this by constructing storyline trees, hierarchical representations that organize narratives from global themes and major plotlines to fine-grained events. We first segment chapters into contiguous narrative segments, or scenes, and use them as the basic units for tree construction. We then infer storyline trees through complementary top-down and bottom-up procedures that derive, refine, cluster, and summarize storylines at multiple levels of abstraction. We showcase the utility of this representation for question answering: storyline trees enable adaptive retrieval, allowing models to iteratively inspect high-level narrative structure and retrieve scene-level evidence on demand. Experiments on three long-context narrative QA benchmarks show that adaptive retrieval outperforms strong baselines, including post-trained long-context models and agentic chunk-based methods. Ablations confirm that scenes are more effective basic units than chapters or generic segmentation, and that gains persist under matched retrieval budgets.
Anthology ID:
2026.findings-emnlp.340
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
7140–7160
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.340/
DOI:
Bibkey:
Cite (ACL):
Litu Ou and Mirella Lapata. 2026. Storyline Trees: Hierarchical Representations for Long-Form Narratives. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 7140–7160, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Storyline Trees: Hierarchical Representations for Long-Form Narratives (Ou & Lapata, Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.340.pdf