Visual comparison of hierarchies with inherited attributes: application to multi-regional MRL standards in food safety

The Maximum Residue Limit (MRL) standard specifies the permissible pesticide residues in various types of foods, with limit values determined by foods and inheritance rules in their classification. Comparing both food classification trees and the values of inherited attributes across multi-regional MRL standards is a complex, unresolved challenge. This paper introduces a visualization-based method for comparing multiple hierarchies with inherited attribute values (HIAC) for MRL standards. First, we construct MRL trees (MRLtree) in different regions for each pesticide, recursively assigning values based on food classification and inheritance rules. These MRLtrees are merged into a unified tree (UniMRLtree) by visual modeling for comparative analysis. Second, we propose two visualization design solutions, "UniMRLtree for multiple regions" and "MRL values matrix heatmap" for comparing differences across multi-regional MRL standards. Finally, we present MRLvis, a visual analytics system that supports users to compare and analyze multiple regional MRL standards from multiple perspectives, including food classification and MRL values. A case study involving six global regions demonstrates the method's effectiveness.