Knowledge Base Cleaning Pipeline

About 1360 wordsAbout 5 min

2025-07-05

1. Overview

The core objective of the knowledge base cleaning pipeline is to provide end-to-end information extraction, normalization, and necessary metadata generation services for raw documents provided by users, which often come in heterogeneous formats and contain high levels of informational noise. The extracted data can be directly used for RAG, pre-training, and various downstream tasks for large language models. Additionally, the pipeline converts the cleaned knowledge into a set of Multi-Hop QAs using a sliding window approach. According to experiments from MIRIAD, this QA-formatted knowledge significantly enhances the accuracy of RAG-based reasoning.

The knowledge base cleaning pipeline supports the following file formats: PDF, Markdown, HTML, and webpage information crawled from URLs.

The main workflow of the pipeline includes:

Information Extraction: Utilizing tools like MinerU and trafilatura to extract textual information from raw documents.
Text Segmentation: Using chonkie to split the text into segments, supporting segmentation by tokens, characters, sentences, and other methods.
Knowledge Cleaning: Cleaning the raw textual information by removing redundant tags, correcting formatting errors, and filtering out private or non-compliant content to make the text cleaner and more usable.
QA Construction: Employing a sliding window of three sentences to transform the cleaned knowledge base into a series of multi-step reasoning QAs, which further improves the accuracy of RAG-based reasoning.

2. Pipeline Designing

1. Information Extraction

The first step of the pipeline is to extract textual knowledge from users' original documents or URLs using FileOrURLToMarkdownConverter. This step is crucial as it converts various formats of raw documents into unified markdown text, facilitating subsequent cleaning processes.

conda create -n dataflow python=3.10
conda activate dataflow
git clone https://github.com/OpenDCAI/DataFlow.git
cd DataFlow
pip install -e .
pip install 'mineru[all]'

PDF file extraction in this system is based on MinerU, and requires additional configuration. Users can configure it using the following steps.

Using the Local Model
To run the MinerU model locally, you need to first download the model files to your local storage. MinerU provides an interactive command-line tool to simplify this process.
1. Download Tool Guide:
You can view the help information for the model download tool using the following command:
mineru-models-download --help
2. Start the Model Download:
Run the following command to begin the download process:
mineru-models-download
During the download process, you will encounter the following interactive prompts:
Choose Model Download Source:
Please select the model download source: (huggingface, modelscope) [huggingface]:
It is recommended to choose modelscope as the source for a better download experience.
Select MinerU Version:
MinerU1 uses a pipeline approach — slower but with lower GPU memory requirements. MinerU2.5 uses a vlm (Vision-Language Model) approach — faster but requires more GPU memory. Users can choose the MinerU version based on their needs and download it locally.
Please select the model type to download: (pipeline, vlm, all) [all]:
It is recommended to choose the vlm (MinerU2) version for faster parsing. If you have strict GPU memory limitations or prefer the traditional pipeline approach, choose pipeline (MinerU1). You can also select all to download all available versions.
3. Model Path Configuration
The mineru.json configuration file will be automatically generated when you run the mineru-models-download command for the first time. After the download completes, the local path to the model will be displayed in the terminal and automatically written to your mineru.json file in your user directory for future use.
4. Environment Verification
You can verify your setup using the simplest command-line call:
mineru -p <input_path> -o <output_path> -b <MinerU_Backend> --source local
<input_path>: Local PDF/image file or directory (./demo.pdf or ./image_dir)
<output_path>: Output directory
<mineru_backend>: Backend engine of the MinerU version. For MinerU2.5, set MinerU_Backend to "vlm-vllm-engine"or"vlm-transformers"or"vlm-http-client"; for MinerU1, set it to "pipeline".
5. Tool Usage
The FileOrURLToMarkdownConverter operator allows you to choose the desired backend engine of MinerU.
If using MinerU1: set the MinerU_Backend parameter to "pipeline", which uses the traditional pipeline approach.
If using MinerU2.5 (recommended by default): set the MinerU_Backend parameter to "vlm-vllm-engine"or"vlm-transformers"or"vlm-http-client" to enable the vision-language model engine.
self.knowledge_cleaning_step1 = FileOrURLToMarkdownConverter(
   intermediate_dir="../example_data/KBCleaningPipeline/raw/",
   lang="en",
   mineru_backend="vlm-sglang-engine",
   raw_file = raw_file,
)
🌟 More Info: For detailed information about MinerU, please refer to its GitHub repository: MinerU Official Documentation

Input: Original document files or URL (Using MinerU2) Output: Extracted markdown text

Example:

self.knowledge_cleaning_step1 = FileOrURLToMarkdownConverterBatch(
    intermediate_dir="../example_data/KBCleaningPipeline/raw/",
    lang="en",
    mineru_backend="vlm-vllm-engine",
)
self.knowledge_cleaning_step1.run(
    storage=self.storage.step(),
    # input_key=,
    # output_key=,
)

2. Text Chunking

After document extraction, the text chunking step(KBCChunkGenerator) divides the extracted long text into chunks. The system supports chunking by token, character, sentence, or semantic dimensions.

Input: Extracted Markdown text Output: Chunked JSON file

Example:

text_splitter = KBCChunkGenerator(
    split_method="token",
    chunk_size=512,
    tokenizer_name="Qwen/Qwen2.5-7B-Instruct",
)
text_splitter.run(
    storage=self.storage.step(),
    input_file=extracted,
    output_key="raw_content",
)

3. Knowledge Cleaning

After text chunking, the Knowledge Cleaning(KBCTextCleaner) specializes in standardizing raw knowledge content for RAG (Retrieval-Augmented Generation) systems. This process utilizes large language model interfaces to intelligently clean and format unstructured knowledge, improving the accuracy and readability of the knowledge base.

Input: Chunked JSON file Output: Cleaned JSON file

knowledge_cleaner = KBCTextCleaner(
    llm_serving=api_llm_serving,
    lang="en"
)
knowledge_cleaner.run(
  storage=self.storage.step(),
  input_key= "raw_content",
  output_key="cleaned",
)

4. QA Generation

After knowledge cleaning, the MultiHop-QA Generation(KBCMultiHopQAGenerator) specializes in automatically generating multi-step reasoning question-answer pairs from text data. This process uses large language model interfaces for intelligent text analysis and complex question construction, suitable for building high-quality multi-hop QA datasets. According to experiments from MIRIAD, this QA-formatted knowledge significantly enhances RAG reasoning accuracy.

Input: JSON-formatted plain text Output: For each text segment, generates a set of multi-hop QAs (output in JSON format)

Usage Example:

self.knowledge_cleaning_step4 = Text2MultiHopQAGenerator(
    llm_serving=self.llm_serving,
    lang="en",
    num_q = 5
)
self.knowledge_cleaning_step4.run(
    storage=self.storage.step(),
    # input_key=,
    # output_key=,
)

3. Execution Examples

Users can execute the following scripts to meet different data requirements. Note that scripts under gpu_pipelines, api_pipelines, and cpu_pipelines are respectively suitable for test machines with GPU, user-configured API, and other scenarios.

With Dataflow[vllm], you can run the gpu_pipelines/*_vllm.py scripts, while with Dataflow[sglang], you can run the gpu_pipelines/*_sglang.py scripts.

Knowledge base cleaning and construction for PDF files:

python api_pipelines/kbcleaning_pipeline.py  # API版本
python gpu_pipelines/kbcleaning/kbcleaning_pipeline_vllm.py 
python gpu_pipelines/kbcleaningkbcleaning_pipeline_sglang.py

kbcleaning_pipeline.py kbcleaning_pipeline_pdf_vllm.py kbcleaning_pipeline_pdf_sglang.py

4. Pipeline Example

The following provides an example pipeline configured for the Dataflow[vllm] environment, demonstrating how to use multiple operators for knowledge base cleaning. This example shows how to initialize a knowledge base cleaning pipeline and sequentially execute each extraction and cleaning step.

from dataflow.operators.knowledge_cleaning import (
    KBCChunkGenerator,
    FileOrURLToMarkdownConverterBatch,
    KBCTextCleaner,
    # KBCMultiHopQAGenerator,
)
from dataflow.operators.core_text import Text2MultiHopQAGenerator
from dataflow.utils.storage import FileStorage
from dataflow.serving import LocalModelLLMServing_vllm

class KBCleaning_PDFvllm_GPUPipeline():
    def __init__(self):

        self.storage = FileStorage(
            first_entry_file_name="../../example_data/KBCleaningPipeline/kbc_test.jsonl",
            cache_path="./.cache/gpu",
            file_name_prefix="knowledge_cleaning_step_vllm_engine",
            cache_type="json",
        )

        self.knowledge_cleaning_step1 = FileOrURLToMarkdownConverterBatch(
            intermediate_dir="../../example_data/KBCleaningPipeline/raw/",
            lang="en",
            mineru_backend="vlm-vllm-engine",
        )

        self.knowledge_cleaning_step2 = KBCChunkGenerator(
            split_method="token",
            chunk_size=512,
            tokenizer_name="Qwen/Qwen2.5-7B-Instruct",
        )

    def forward(self):
        self.knowledge_cleaning_step1.run(
            storage=self.storage.step(),
            # input_key=
            # output_key=
        )
        
        self.knowledge_cleaning_step2.run(
            storage=self.storage.step(),
            # input_key=
            # output_key=
        )

        self.llm_serving = LocalModelLLMServing_vllm(
            hf_model_name_or_path="Qwen/Qwen2.5-7B-Instruct",
            vllm_max_tokens=2048,
            vllm_tensor_parallel_size=4,
            vllm_gpu_memory_utilization=0.6,
            vllm_repetition_penalty=1.2
        )

        self.knowledge_cleaning_step3 = KBCTextCleaner(
            llm_serving=self.llm_serving,
            lang="en"
        )

        self.knowledge_cleaning_step4 = Text2MultiHopQAGenerator(
            llm_serving=self.llm_serving,
            lang="en",
            num_q = 5
        )

        self.knowledge_cleaning_step3.run(
            storage=self.storage.step(),
            # input_key=
            # output_key=
        )
        self.knowledge_cleaning_step4.run(
            storage=self.storage.step(),
            # input_key=
            # output_key=
        )
        
if __name__ == "__main__":
    model = KBCleaning_PDFvllm_GPUPipeline()
    model.forward()