Mitigating Hallucination and Omission in LLM-Based Machine Translation Using Word Alignment Preference

Concetti Chiave

Leveraging word alignment as a preference signal during optimization can effectively reduce hallucination and omission errors in Large Language Model (LLM)-based machine translation systems.

Sintesi

Wu, Q., Nagata, M., Miao, Z., & Tsuruoka, Y. (2024). Word Alignment as Preference for Machine Translation. arXiv preprint arXiv:2405.09223v2.

This research paper investigates the potential of using word alignment as a preference signal to mitigate the prevalent issues of hallucination and omission in LLM-based machine translation systems.

Approfondimenti chiave tratti da

Word Alignment as Preference for Machine Translation

by Qiyu Wu, Mas... alle arxiv.org 11-22-2024

https://arxiv.org/pdf/2405.09223.pdf

Domande più approfondite

How can the reliance on potentially imperfect word alignment models be further minimized in the WAP framework to improve its robustness and accuracy?

Minimizing the reliance on imperfect word alignment models in the WAP framework is crucial for enhancing its robustness and accuracy in mitigating hallucination and omission in machine translation (MT). Here are several strategies:

Ensemble Word Alignment: Instead of relying on a single word aligner, leverage an ensemble of multiple word aligners trained on diverse datasets and using different architectures. This can help to mitigate the impact of errors made by individual aligners, as the ensemble can produce a more robust and accurate alignment by combining their predictions.

Contextualized Word Embeddings: Utilize advanced word alignment models that incorporate contextualized word embeddings, such as BERT or XLMR. These models can capture richer semantic and contextual information, leading to more accurate word alignments, especially in cases of ambiguity or complex sentence structures.

Joint Training with MT Model: Explore joint training of the word alignment model and the LLM-based MT model. This allows for end-to-end optimization, where the word alignment model can learn to produce alignments that are specifically tailored to improve the MT model's performance in terms of reducing hallucination and omission.

Reinforcement Learning for Alignment: Investigate the use of reinforcement learning (RL) to train word alignment models that directly optimize for MT quality metrics, such as BLEU or COMET, or even task-specific metrics related to hallucination and omission. RL can enable the aligner to learn from the feedback of the MT model and improve its alignment decisions over time.

Iterative Refinement with Cross-Lingual Constraints: Implement an iterative refinement process where initial word alignments are iteratively refined using cross-lingual constraints. These constraints can include linguistic rules, semantic similarity measures, or even feedback from the MT model itself. This iterative process can help to correct alignment errors and improve the overall accuracy.

By incorporating these strategies, the WAP framework can become more robust to the imperfections of individual word alignment models, leading to more reliable and accurate mitigation of hallucination and omission in LLM-based MT.

Could alternative evaluation metrics, specifically designed to capture the nuances of hallucination and omission in MT, provide a more comprehensive assessment of the proposed method's effectiveness compared to BLEU and COMET?

Yes, alternative evaluation metrics specifically designed to capture the nuances of hallucination and omission in MT can provide a more comprehensive assessment of the proposed method's effectiveness compared to general-purpose metrics like BLEU and COMET.
Here's why:

BLEU and COMET's limitations: While BLEU and COMET are widely used, they primarily focus on lexical overlap and semantic similarity with reference translations. They are not sensitive enough to directly penalize hallucinations (added content) or omissions (missing content) that might not significantly affect the overall semantic meaning.

Need for targeted metrics: To accurately evaluate the mitigation of hallucination and omission, we need metrics that explicitly quantify these phenomena. These metrics should be able to:

Identify and penalize hallucinated content: Measure the extent of extraneous information generated by the MT model that is not present in the source text.
Detect and quantify omitted content: Assess the amount of information from the source text that is missing in the translation.
Examples of alternative metrics:

Hallucination Ratio (HR): Calculate the ratio of hallucinated words (not aligned to any source words) to the total number of words in the translation. A lower HR indicates better performance in mitigating hallucinations.
Omission Ratio (OR): Compute the ratio of omitted words (source words with no alignment in the translation) to the total number of words in the source text. A lower OR indicates better performance in mitigating omissions.
Coverage-Adjusted BLEU (CAB): Modify BLEU to incorporate a penalty term based on the coverage score, which reflects the proportion of source words aligned to the translation. This encourages translations with higher coverage, thus reducing omissions.
Semantic Similarity with Hallucination and Omission Penalties (SS-HOP): Combine semantic similarity measures with explicit penalties for hallucinated and omitted content. This provides a more balanced evaluation that considers both semantic adequacy and faithfulness to the source text.
By employing these alternative metrics alongside BLEU and COMET, we can gain a more comprehensive understanding of the proposed method's effectiveness in specifically addressing hallucination and omission in LLM-based MT.

How can the principles of word alignment preference be applied to other NLP tasks beyond machine translation, particularly those susceptible to similar issues of generating factually inconsistent or incomplete outputs?

The principles of word alignment preference, which leverage the alignment between source and target text to guide model training towards more faithful and complete outputs, can be extended to various NLP tasks beyond machine translation. Here are some examples:
1. Text Summarization:

Problem: Summarization models can generate summaries that contain factual inconsistencies (hallucinations) or miss crucial information from the source document (omissions).
Solution: Train summarization models with a preference for summaries that exhibit high word alignment scores with the source document. This encourages the model to generate summaries that are grounded in the original text and less likely to hallucinate or omit important details.
2. Question Answering:

Problem: Question answering (QA) systems can provide answers that are not supported by the given context (hallucinations) or fail to address all aspects of the question (omissions).
Solution: Incorporate word alignment preference during training to favor QA models that generate answers with strong alignment to relevant segments in the context. This promotes answer faithfulness and completeness.
3. Dialogue Generation:

Problem: Dialogue models can produce responses that are factually incorrect (hallucinations) or lack coherence with the conversation history (omissions).
Solution: Train dialogue models with a preference for responses that align well with relevant information from the dialogue history. This encourages the model to generate consistent and contextually appropriate responses.
4. Data-to-Text Generation:

Problem: Models that generate text from structured data can produce outputs that contain factual errors (hallucinations) or miss important data points (omissions).
Solution: Utilize word alignment preference to guide the model towards generating text that accurately reflects all relevant information from the input data.
General Approach:

Define Alignment: Adapt the concept of word alignment to the specific task. For instance, in summarization, alignment could be between words in the summary and sentences in the source document.
Generate Preference Data: Create training data with preferred and rejected outputs based on their alignment scores, similar to the WAP framework.
Preference-Based Training: Train the model using preference learning techniques, such as DPO, to optimize for the preferred outputs with higher alignment scores.

By applying these principles, we can leverage the power of word alignment preference to improve the factual consistency and completeness of various NLP models, leading to more reliable and trustworthy AI systems.