Evaluating Factuality in Generation with Dependency-level Entailment
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/2020.findings-emnlp.322.pdf
Summary
Neural text generators often produce fluent output that contradicts their source. Sentence-level entailment classifiers have been used to filter such output, but they were trained for a different task and cannot show where an error occurs. Goyal and Durrett propose Dependency Arc Entailment (DAE), which splits factuality checking into many small decisions. For each arc in the dependency parse of the generated sentence, a binary classifier asks whether the source supports the relation between head and child. The model encodes the source and hypothesis together with a pre-trained encoder. Each arc is represented by its head token, its child token, and an embedding of its label. Human arc-level labels are hard to collect, so the authors build training labels automatically from paraphrase data. On summarization and paraphrase test sets, DAE detects factual inconsistencies better than sentence-level entailment and question-generation/answering methods. It also flags the specific faulty arcs, which makes its judgments easier to interpret.
Key points
- Each arc gets one of two labels, entailed or non-entailed. Relations that NLI would call neutral or contradictory both count as non-entailed. Arcs come from a filtered set of Stanford Enhanced Dependencies, with punctuation and similar weakly semantic arcs removed.
- Arc representation: the contextual embeddings of the head and child tokens plus a dependency-label embedding, passed to a linear layer with softmax. Training uses binary cross-entropy.
- Supervision is derived automatically from the ParaNMT-50M paraphrase corpus, which was itself built by noisy backtranslation. Evaluation covers the summarization test set of Falke et al. (2019) and a paraphrase test set. Data and code: github.com/tagoyal/dae-factuality.
- In qualitative examples, an MNLI model assigns about 99% entailment to outputs where subject–object roles are swapped, while DAE gives the swapped arcs low scores.
- Limitations:
- Negation and quantification are not marked on arcs.
- Information omitted from the output cannot be detected.
- The model is weaker on synonym substitutions than on hallucinations or changes in argument structure.
Cited by
- CLIFF: Contrastive Learning for Improving Faithfulness and Factuality in Abstractive Summarization
- QAFactEval: Improved QA-Based Factual Consistency Evaluation for Summarization
- Annotating and Modeling Fine-grained Factuality in Summarization
- Evaluating Large Language Models: A Comprehensive Survey
- A Survey on Hallucination in Large Language Models: Principles, Taxonomy, Challenges, and Open Questions
- Survey of Hallucination in Natural Language Generation
- ChatGPT as a Factual Inconsistency Evaluator for Text Summarization
- Understanding Factuality in Abstractive Summarization with FRANK: A Benchmark for Factuality Metrics
- MiniCheck: Efficient Fact-Checking of LLMs on Grounding Documents
- AlignScore: Evaluating Factual Consistency with A Unified Alignment Function
Cite
@inproceedings{goyal2020evaluating,
title = {{Evaluating Factuality in Generation with Dependency-level Entailment}},
author = {Goyal, Tanya and Durrett, Greg},
booktitle = {Findings of the Association for Computational Linguistics: EMNLP 2020},
year = {2020},
doi = {10.18653/v1/2020.findings-emnlp.322},
url = {https://doi.org/10.18653/v1/2020.findings-emnlp.322}
}References
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