WCAG-ODC: an orthogonal defect classification framework for web accessibility defects

Web accessibility evaluation tools are widely used to detect compliance issues with the Web Content Accessibility Guidelines (WCAG), yet their outputs often consist of fragmented rule-level findings that provide limited support for structured analysis and remediation prioritization. This paper introduces WCAG-ODC, a structured framework that adapts Orthogonal Defect Classification (ODC) principles to accessibility defect analysis. The framework transforms raw accessibility findings into structured defect representations using a cause–effect attribute model incorporating defect type, WCAG principle, source element, detection trigger, severity, and impact area. WCAG-ODC was evaluated through a case study of nine public e-services using accessibility findings collected from multiple automated accessibility evaluation tools, with defect-level classification performed on the IBM Equal Access Toolkit dataset. A defect-level dataset of 2,590 accessibility records was constructed and mapped into 31 rule categories and nine higher-level defect families. The results show that Keyboard Access, Interactive Controls, and Structure and Navigation defects dominate the dataset, while severity and impact-area analyses reveal clear relationships between technical defect families and user-facing accessibility barriers. The findings demonstrate that WCAG-ODC enables accessibility defects to be analyzed beyond aggregated tool counts by supporting defect-family analysis, severity profiling, impact mapping, and remediation prioritization. The study concludes that WCAG-ODC provides a systematic and reproducible foundation for accessibility defect classification and accessibility-oriented software quality improvement. Independent coding validation demonstrated almost perfect agreement for Defect Type classification ( $$\kappa$$ = 0.922), supporting the reliability and reproducibility of the proposed framework.