---
license: llama3
base_model:
- meta-llama/Meta-Llama-3-8B-Instruct
tags:
- question_answering
- fine_tuned
- lora
- explainability
---
# Llama3-8B-Instruct Fine-tuned for QED (Question-Explanation-Data)

## Model Description

This model is a fine-tuned version of [meta-llama/Meta-Llama-3-8B-Instruct](https://huggingface.co/meta-llama/Meta-Llama-3-8B-Instruct) specifically adapted for the QED (Question-Explanation-Data) task. The model has been trained to provide structured explanations for question answering by generating three key components simultaneously: direct answers, supporting sentences, and referential entity mappings.

## Task Overview

The QED task, introduced in ["A Framework and Dataset for Explanations in Question Answering"](https://direct.mit.edu/tacl/article/doi/10.1162/tacl_a_00398/106795/QED-A-Framework-and-Dataset-for-Explanations-in), requires models to:

1. **Answer Extraction**: Identify the shortest span from a passage that directly answers a given question
2. **Evidence Selection**: Select the single sentence from the passage that best entails or implies the answer
3. **Referential Mapping**: Establish connections between entities mentioned in the question and their corresponding references in the selected sentence

## Fine-tuning Details

- **Base Model**: meta-llama/Meta-Llama-3-8B-Instruct
- **Fine-tuning Method**: LoRA (Low-Rank Adaptation) with rank=16, alpha=32
- **Quantization**: 4-bit quantization for memory efficiency
- **Training Strategy**: Few-shot learning with "random_two" example prompting
- **Training Data**: Curated subset of QED training examples
- **Output Format**: Structured JSON containing answer, selected_sentence, and referential_equalities

## Performance Improvements

Significant improvements over the base model on QED evaluation metrics:

| Metric | Base Model (Zero-shot) | Fine-tuned Model | Improvement |
|--------|------------------------|------------------|-------------|
| Exact Match Accuracy | 0.9% | **11.8%** | **+10.9%** |
| Answer Accuracy | 82.0% | **86.4%** | **+4.4%** |
| All Mention F1 | 5.5% | **38.4%** | **+32.9%** |
| Question Mention F1 | 6.0% | **47.6%** | **+41.6%** |
| Context Mention F1 | 5.0% | **29.2%** | **+24.2%** |

*Results based on 0.5 F1 overlap threshold, non-strict matching*

## Training Code & Methodology

This model was trained using our comprehensive QED fine-tuning framework available on GitHub:

**🔗 [QED Fine-Tuning Framework](https://github.com/denisrize/QED-LLM-ExplanationGeneration/tree/main)**

## Usage

The model expects input in a specific format and outputs structured JSON:

```python
# Input format
prompt = """
Title: [Document Title]
Question: [Your Question]
Passage: [Context Passage]

You are an expert at extracting answers and structured explanations from text.
Your response MUST be **valid JSON only** (no extra commentary).

Task
====
Given:
• a **title** for the passage,
• a **question** about the passage, and
• the **context passage** itself,

produce an explanation object with three parts:

1. "answer" – the **shortest span** from the passage that fully answers the question.
2. "selected_sentence" – the **single sentence** in the passage that entails or implies the answer.
3. "referential_equalities" – a list of mappings between phrases in the question and phrases in the selected sentence
   that refer to the **same real-world entity/event**.

   • Each mapping has two keys:
       - "question_reference": the exact phrase from the question (**must be a contiguous substring from the question,
          not from the context or title**).
       - "sentence_reference": the exact phrase from the selected sentence (**must be a contiguous substring from the selected sentence,
          not from the question or title**), or "" (empty string if the entire sentence is the referent).

     ▸ Use **""** for "sentence_reference" when the entity/event is not named by any specific phrase in the sentence –
       i.e. the entire sentence acts as the referent (a *bridge* to the whole sentence).  
       This corresponds to the (start = end = -1) convention in the QED dataset.

Output format
=============
Return **only** JSON in this exact schema:

{
  "answer": "<string from passage>",
  "selected_sentence": "<string from passage>",
  "referential_equalities": [
    {
      "question_reference": "<string from question only>",
      "sentence_reference": "<string from selected_sentence only, or "">",
      "bridge": "<false if not a bridge; otherwise, a string explaining the bridge connection, e.g., 'in', 'for', 'of', 'at', 'on'>"
    }
    ...
  ]
}
"""

# Expected output format
{
  "answer": "<shortest span from passage>",
  "selected_sentence": "<sentence that entails the answer>",
  "referential_equalities": [
    {
      "question_reference": "<entity from question>",
      "sentence_reference": "<corresponding entity from sentence>",
      "bridge": false
    }
  ]
}
```

## Evaluation

Evaluated on the QED development set with official metrics across multiple overlap thresholds (0.5-0.9). The model shows consistent improvements in all measured aspects of the QED task, particularly excelling at entity reference mapping and answer extraction.

## Training Details

- **Dataset**: QED training subset with careful example curation
- **Learning Rate**: 5e-6 with warmup ratio of 0.2
- **Batch Size**: Effective batch size of 16 through gradient accumulation
- **Optimizer**: Paged AdamW 8-bit for memory efficiency
- **Evaluation**: Multi-threshold validation (0.5-0.9 F1 overlap)
- **Epochs**: 3 Epochs

## Applications

This model is particularly suitable for:
- Educational question answering systems requiring explanations
- Research applications needing interpretable QA
- Systems where answer provenance and entity tracking are important
- Building more transparent and accountable AI assistants

## Citation

Please cite the original QED work when using this model:

```bibtex
@article{lamm2020qed,
  title={QED: A Framework and Dataset for Explanations in Question Answering},
  author={Lamm, Matthew and Palomaki, Jennimaria and Alberti, Chris and Andor, Daniel and Chen, Eunsol and Devlin, Jacob and Michael, Julian},
  journal={arXiv preprint arXiv:2010.13806},
  year={2020}
}
```
```