Measure property data quality using completeness (60%) + confidence (40%) formula. Quality tiers are Excellent (95%+), Good (80-94%), Fair (60-79%), Poor (<60%). Track field lineage by source (Assessor 0.95, CSV 0.90, Web 0.75, AI 0.70). Use when calculating data completeness, tracking field provenance, enforcing CI/CD quality gates, or generating data quality reports.