Abstract:

Accurate software cost estimation depends on sizing methods that capture the full scope of project requirements, including non-functional requirements such as accessibility. This study examines whether three established sizing frameworks, Use Case Points (UCP), COSMIC Function Points, and IFPUG SNAP, operationalise accessibility as a non-functional requirement. Accessibility, commonly operationalised through conformance with WCAG guidelines (W3C, 2023), generates specific, verifiable implementation effort across multiple development phases, yet it is rarely treated as a formal cost driver in sizing models. The study uses document analysis of the normative sources for each framework. The findings are consistent across all three: none provides an explicit classification mechanism, counting rules, complexity parameters, or a calculation procedure for accessibility requirements. In SNAP, the most relevant framework, as it is specifically designed for non-functional requirements, accessibility appears in the ISO 25010 quality model as a sub-characteristic of Usability and in the normative document as a one-time disclaimer, but is not operationalised as a distinct, reproducible measurement construct. The issue is not that accessibility cannot be associated with existing categories, but that the Assessment Practices Manual provides no explicit, reproducible procedure for doing so. Two of the three frameworks have formal structural extension points that could accommodate accessibility: COSMIC through its open NFR slots, and SNAP through its ISO 25010 mapping structure. UCP has no formally documented extension mechanism, though its factor list is not explicitly closed to additions. The absence of accessibility from these frameworks may contribute to systematic underestimation of accessibility costs in software projects.