When chunking lengthy legal documents for vectorization, focus on preserving logical structure, maintaining context, and enabling accurate retrieval. Legal texts often contain nested sections, cross-references, and precise terminology, so your chunking strategy should balance readability with machine processing needs. Start by analyzing the document’s inherent structure—use natural breaks like sections, subsections, and paragraphs as chunk boundaries. For example, a contract might be divided into “Definitions,” “Obligations,” and “Termination” clauses, each serving as a standalone chunk. Keep chunks under 512 tokens (a common limit for many embedding models) to avoid truncation and ensure compatibility with downstream tools.
Overlap chunks strategically to retain context where critical concepts span multiple sections. For instance, if a “Liability” clause references a “Confidentiality” section from an earlier chunk, include 10-15% of the previous text in the next chunk to preserve relationships. However, avoid excessive overlap to prevent redundant embeddings. Tools like LangChain’s text splitters or custom regex-based parsers can automate this by sliding a window across the text. For tables or numbered lists, treat them as atomic units—splitting them mid-structure could invalidate their meaning. Always validate chunk sizes post-splitting using tokenizers matching your embedding model (e.g., Hugging Face’s transformers for BERT-based models).
Include metadata to enhance search accuracy. Attach section titles, page numbers, or document IDs to each chunk, enabling filters during retrieval. For example, a chunk from a patent document might include metadata like {"section": "Claims", "patent_id": "US-12345"}. If using PDFs, extract text with layout-aware tools like PyPDF2 or pdfplumber to retain headings and indentations as structural cues. Finally, test the chunked output with sample queries to ensure the model can retrieve relevant sections. If a query about “termination notice periods” consistently misses the correct clause, adjust chunk boundaries or metadata tagging to improve alignment.