Towards Generative Event Factuality Prediction
Paper · 2023 · John Murzaku, Tyler Osborne, Amittai Aviram et al.
Summary
Most work on event factuality asks only how the author presents an event: as certain, possible, unknown, or not happened. This paper extends the task to factuality attributed to sources mentioned inside the text, such as a person who "said" something. The authors use FactBank, an expert-annotated newswire corpus and the only one with nested-source annotation. They build a database representation of it and derive two tasks: source-and-target factuality (STF) and author-only factuality (AOF).
Each judgment is encoded as a triple of source head word, target event head word and one of five factuality values. Flan-T5-base is fine-tuned to generate these structures end to end, without gold event heads. The authors compare output formats, such as tuple/triplet strings against in-line annotation of the sentence. They also test task prefixes and multi-task mixtures with other corpora.
Careful output formatting and suitable multi-task mixtures both help. The system sets new state-of-the-art end-to-end results on FactBank author-only factuality and gives the first results for source-and-target factuality. This matters because a reader must separate what the author asserts from what others are reported to believe.
Key points
- Factuality labels are reduced to five values: CT+, CT-, PR+, PR- and UU. The FactBank distinction between probable and possible is merged to reduce data fragmentation.
- A judgment is a (source, target, value) triple over syntactic head words, with a special AUTHOR token for the writer. The nested chain of sources (Author → Mary → John) is collapsed to the last source only.
- The model is Flan-T5-base. Tuple/triplet output beats in-line annotation ("Anno") in exact-match evaluation, mainly because Anno does worse on the frequent CT+ label.
- On FactBank author-only, the best exact-match F1 is 0.897, from multi-task learning with the FBST data (FBAO*, FBST). The plain FBAO setting reaches 0.866. AOF scores about 13.3 points absolute above STF.
- Other author-only corpora are surveyed and used for combinations: LU, UW, LDCCB, MEANTIME, MegaVeridicality, UDS-IH2, CommitmentBank and RP.
Interesting ideas
- I1. Representing "who presents which event as how factual" as a small triple anchored on head words gives a compact, checkable target that could be reused for any attribution-style annotation.
- I2. The authors merge hard-to-separate categories (probable vs. possible), trading granularity for more reliable labels and less sparse data, which suits small corpora.
- I3. Choosing the output format of a generative model is treated as a design variable, and structured tuples beat in-line markup on the frequent cases.
- I4. The same system is reported under both a macro-average and an exact-match micro metric, which reveals different strengths (Anno helps rare labels but hurts overall).
- I5. Keeping the author's commitment separate from a reported source's commitment avoids treating reported claims as facts in the text's world.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (frames): prag could attach a factuality triple (AUTHOR or speaker-entity, event head, CT+/PR+/UU…) to every frame produced under verbs like say or believe.
- I2 (world): world states could carry a coarse certainty scale (certain/possible/unknown × polarity) instead of fine grades that are hard to justify.
- I3 (learn): when the LLM teacher produces silver labels, asking for explicit tuples rather than annotated sentences may give cleaner, easier-to-verify supervision.
- I4 (learn): evaluations could routinely report both a per-label macro score and an exact-match score, so that gains on rare classes do not hide losses on common ones.
- I5 (answer): QA on fables and tales could answer "did X happen?" differently from "did the fox say X happened?", using the source in the stored triple.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksArts and Humanities · 16,039 worksLanguage and Linguistics · 15,891 works
Cite
Cite as John Murzaku, Tyler Osborne, Amittai Aviram and Owen Rambow. 2023. Towards Generative Event Factuality Prediction. Findings of the Association for Computational Linguistics: ACL 2023.
@inproceedings{murzaku2023generative,
title = {{Towards Generative Event Factuality Prediction}},
author = {John Murzaku, Tyler Osborne, Amittai Aviram and Owen Rambow},
booktitle = {Findings of the Association for Computational Linguistics: ACL 2023},
year = {2023},
doi = {10.18653/v1/2023.findings-acl.44},
url = {https://doi.org/10.18653/v1/2023.findings-acl.44}
}References
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