Convention-Level Pattern Analysis of Exemptions and Equivalents in IMO Regulations using Rule-Based Pipeline

This study examines how flag states utilize exemptions and equivalents within the International Maritime Organization's regulatory system, using ten years of cleaned and enriched Global Integrated Shipping Information System (GISIS) notifications.Data preparation used a deterministic, rule-based pipeline that transformed semi-structured text through tokenization, regex patterning, and n-gram co-occurrence analysis.Standardized instrument references and reconstructed analytical fields were linked to metadata on ship type and size.The Analyses examined exemption intensity, cross-flag variation, convention portfolios, ship-type associations, temporal dynamics, and exploratory clustering.Results show that exemptions are concentrated in technical regimes led by International Convention for the Safety of Life at Sea, followed by International Convention for the Prevention of Pollution from Ships, International Regulations for Preventing Collisions at Sea, and International Convention on Load Lines; national portfolios are coherent rather than random; and volumes increase over the decade despite adjustment for exposure.Notification rates remain highly right-skewed, with a small subset of flags accounting for a disproportionate share of documented exemptions and equivalents.Methodologically, the paper contributes a reproducible, deterministic pipeline that normalizes instrument references, reconstructs exemption fields, and links notifications to vessel attributes, enabling exposure-adjusted cross-flag comparisons and portfolio analysis.The scope is limited to convention-level categories rather than clause-or rule-specific analyses because citation patterns in flag-state reports are fragmented and heterogeneous.Findings have implications for transparency, comparability, and the design of structured reporting in GISIS to support evidencebased oversight.