蓝图：重建遗产——复杂工程图纸和文档的多模态检索

The study presents Blueprint, a layout-aware multimodal retrieval system designed to address the challenges posed by decades of engineering drawings and technical records locked in legacy archives with inconsistent or missing metadata. Blueprint detects canonical drawing regions, applies region-restricted VLM-based OCR, normalizes identifiers (e.g., DWG, part, facility), and fuses lexical and dense retrieval with a lightweight region-level reranker. Deployed on approximately 770,000 unlabeled files, it automatically generates structured metadata suitable for cross-facility search. The effectiveness of Blueprint is evaluated on a benchmark of 5,000 files with 350 expert-curated queries, using pooled, graded (0/1/2) relevance judgments.