Hybrid Multi-Phase Page Matching and Multi-Layer Diff Detection for Japanese Building Permit Document Review

TL;DR

This paper introduces a hybrid multi-phase page matching and multi-layer diff detection algorithm for automating the comparison of Japanese building permit documents, significantly reducing manual effort and errors.

Contribution

The paper presents a novel multi-phase matching algorithm combined with a multi-layer diff engine tailored for complex Japanese building permit documents.

Findings

Achieved F1 score of 0.80 on real-world data

Attained perfect precision with zero false positives

Effectively handles substantial content and order changes

Abstract

We present a hybrid multi-phase page matching algorithm for automated comparison of Japanese building permit document sets. Building permit review in Japan requires cross-referencing large PDF document sets across revision cycles, a process that is labor-intensive and error-prone when performed manually. The algorithm combines longest common subsequence (LCS) structural alignment, a seven-phase consensus matching pipeline, and a dynamic programming optimal alignment stage to robustly pair pages across revisions even when page order, numbering, or content changes substantially. A subsequent multi-layer diff engine -- comprising text-level, table-level, and pixel-level visual differencing -- produces highlighted difference reports. Evaluation on real-world permit document sets achieves F1=0.80 and precision=1.00 on a manually annotated ground-truth benchmark, with zero false-positive matched pairs.