Newer standards place usability inside a broader quality-in-use concept alongside accessibility, not containing it

What it is

The standard family later re-layered itself: the 2018 revision of ISO 9241-11 and ISO/IEC 25010 situate "usability" within a larger quality-in-use frame, where it stands as a component beside efficiency, satisfaction, accessibility, and risk mitigation—rather than accessibility being a sub-item of usability.

Why it happens

The layering follows judgment independence: accessibility has its own logic of verdicts (assistive-technology compatibility, alternative perceptual channels) that does not overlap the "three specified × three components" frame; folding accessibility into usability systematically produces misses in accessibility review. The parallel structure lets each component carry its own acceptance line and ownership—usability owned by interaction design, accessibility by the accessibility practice—both rolling into the quality-in-use ledger. The terminology shift also moves calibers: the same word covers different scopes across standard versions, so citations must carry version numbers.

Studying it

Studying the standards' impact means document and practice analysis: compare evaluation reports, contract clauses, and instruments (scales, audit checklists) published under old versus new frames for caliber shifts. In measurement, the quality-in-use frame encourages per-component measurement with combined reporting: usability's three components, accessibility conformance, and risk indicators collected separately so a single total score cannot hide accessibility gaps. Methodologically, the independence assumption needs checking—satisfaction and accessibility correlate in practice, so combined reports must still disclose raw scores.

Where it stops holding

The framework layering is convention, not discovery: the parallel structure reflects standards governance, not psychological independence of the components. Terminology mixing persists in industry—"usability" is broad in older usage and narrow in the new one—so cross-document comparison starts with caliber checks. Quality in use is still expanding (safety, well-being components appear), and the frame's own boundary is moving.

Applying it

• Adopt the new layering explicitly in quality documents: usability, accessibility, satisfaction, and others each with their own metrics and acceptance lines, reported together as quality in use.
• Attach standard version numbers when revising definition clauses in contracts and requirement templates to prevent caliber mixing.
• Assign separate owners and budgets to accessibility and usability testing, and present them side by side in reports without converting one into the other.

Related

• Same group: B5.08.1 The standard definition confines usability to specified users, specified goals, and a specified context of use · B5.08.2 Context of use includes device, physical environment, and social environment—not just the interface · B5.08.3 The definition treats usability as a relational property of product and context, not an inherent property of the product
• Nearby: J1 Accessibility and Inclusion · R2 Design Systems and Engineering Delivery
• Search terms: quality in use · iso 25010 · usability accessibility standards