Non-Functional Requirements (NFRs) Framework for Software Systems

Overview

Accessibility Non-Functional Requirements (NFRs) define how a software system must support users with disabilities, assistive technologies, keyboard navigation, readable presentation, understandable interaction, robust implementation, and applicable accessibility standards.

Accessibility is related to usability, but it is not optional and should not be treated as a visual-design enhancement. Accessibility NFRs should define standards, conformance level, supported assistive technologies, validation methods, exception handling, remediation expectations, and release-readiness evidence.

Best Practice: Define accessibility standards and conformance-level non-functional requirements

Description

Accessibility standards and conformance-level NFRs define the specific standard, version, level, scope, and exceptions that apply to the system. They should clearly identify whether the target is, for example, Web Content Accessibility Guidelines (WCAG) Level AA or another applicable organizational, contractual, regulatory, or jurisdictional requirement.

Benefits

Explicit conformance targets prevent vague accessibility requirements, support procurement and compliance review, guide design and testing, and create a defensible basis for release decisions.

Example non-functional requirements

• User-facing web screens shall conform to the approved enterprise accessibility standard and documented conformance level for in-scope content and workflows.

• Validation method: Validate through accessibility audit, standards mapping, design review, manual testing, automated scanning, and release-readiness approval.

• Example validation evidence: Accessibility conformance report, audit checklist, scan report, manual test notes, exception log, and release approval.

Related stakeholders

Typical stakeholders include accessibility specialists, UX designers, product owners, legal/compliance teams, QA teams, developers, procurement teams, and users with disabilities.

Related lifecycle phases

Accessibility standards NFRs are defined during requirements and design; implemented during UX and UI development; validated during accessibility testing and release readiness; and monitored through defect trends, user feedback, and compliance review.

Best Practice: Define Web Content Accessibility Guidelines (WCAG) non-functional requirements

Description

WCAG NFRs translate accessibility principles and success criteria into requirements for web applications, portals, documents, dashboards, forms, media, and other digital content. They should identify the WCAG version, conformance level, in-scope assets, and validation approach.

Benefits

WCAG-aligned requirements improve legal and regulatory defensibility, make accessibility testable, and help teams design inclusive software from the beginning rather than remediating defects late.

Example non-functional requirements

• All new and materially changed user-facing web content shall be evaluated against the approved WCAG version and conformance level before release.

• Validation method: Validate through automated accessibility scans, manual WCAG review, assistive technology testing, and defect remediation verification.

• Example validation evidence: WCAG test report, automated scan output, manual review notes, assistive technology test evidence, and remediation closure record.

Related stakeholders

Typical stakeholders include accessibility specialists, UX designers, front-end developers, QA teams, legal/compliance stakeholders, product owners, and content owners.

Related lifecycle phases

WCAG NFRs are defined during UX and content planning; implemented during UI development; validated during accessibility testing and UAT; and improved during maintenance and regulatory updates.

Best Practice: Define perceivable content and presentation non-functional requirements

Description

Perceivable content NFRs define how users can perceive information through text, structure, alternatives, color, contrast, captions, transcripts, labels, and other presentation patterns. They should ensure that information is not conveyed only through color, position, sound, or visual format.

Benefits

Perceivable content requirements help users with visual, auditory, cognitive, or situational limitations access the same essential information as other users.

Example non-functional requirements

• All informative images, charts, icons, and visual status indicators shall include appropriate text alternatives or accessible descriptions where needed to understand the information.

• Validation method: Validate through content inspection, accessibility scan, screen reader testing, and design review.

• Example validation evidence: Alt text review record, accessibility scan report, screen reader test notes, design review approval, and defect closure evidence.

• Text and meaningful visual indicators shall meet approved contrast requirements in normal, hover, focus, selected, disabled, and error states.

• Validation method: Validate through contrast scanning, design token review, visual inspection, and browser/device testing.

• Example validation evidence: Contrast scan report, design token approval, visual inspection checklist, and cross-browser evidence.

Related stakeholders

Typical stakeholders include UX designers, content owners, accessibility specialists, front-end developers, QA teams, and product owners.

Related lifecycle phases

Perceivable content NFRs are defined during content and design; implemented during UI development; validated through accessibility testing; and monitored through defect reports and user feedback.

Best Practice: Define operable interaction and keyboard navigation non-functional requirements

Description

Operable interaction NFRs define how users can navigate and operate software without relying on a single input method. They should address keyboard access, focus order, visible focus indicators, skip links, timeouts, modal behavior, and avoidance of keyboard traps.

Benefits

Operable interaction requirements are essential for users who rely on keyboards, switch devices, screen readers, voice input, or other assistive technologies. They also improve productivity and resilience for all users.

Example non-functional requirements

• All interactive controls in primary workflows shall be reachable and operable using keyboard-only navigation without keyboard traps.

• Validation method: Validate through keyboard-only testing, focus-order review, assistive technology testing, and UAT with representative workflows.

• Example validation evidence: Keyboard test script, focus-order evidence, screen recording, assistive technology test notes, and defect closure record.

• The system shall provide visible focus indication for all interactive components across supported browsers and themes.

• Validation method: Validate through visual inspection, CSS/design-system review, browser compatibility testing, and accessibility review.

• Example validation evidence: Focus indicator checklist, design-system review, browser test evidence, accessibility approval, and defect log.

Related stakeholders

Typical stakeholders include accessibility specialists, UX designers, front-end developers, QA teams, product owners, and assistive technology users.

Related lifecycle phases

Operable interaction NFRs are defined during interaction design; implemented during front-end development; validated through keyboard, assistive technology, and UAT testing; and improved through user feedback and accessibility defect trends.

Best Practice: Define understandable content, workflow, and error-message non-functional requirements

Description

Understandable accessibility NFRs define how users can comprehend labels, instructions, workflow steps, error messages, help content, and system responses. They should consider plain language, predictable behavior, clear instructions, input assistance, and consistent terminology.

Benefits

Understandable content requirements reduce errors, improve task completion, support cognitive accessibility, and reduce support burden for all users.

Example non-functional requirements

• Required form fields, input formats, and validation rules shall be explained before or at the point of input.

• Validation method: Validate through content review, form workflow testing, accessibility review, and UAT.

• Example validation evidence: Form review checklist, test results, accessibility review notes, UAT feedback, and defect closure record.

• Error messages shall identify the problem, describe how to correct it, and be announced or exposed appropriately to assistive technologies.

• Validation method: Validate through form error testing, screen reader testing, ARIA/live-region inspection where applicable, and UX review.

• Example validation evidence: Error message test results, screen reader notes, markup inspection record, UX approval, and accessibility defect closure.

Related stakeholders

Typical stakeholders include UX writers, content owners, accessibility specialists, business analysts, QA teams, developers, and support teams.

Related lifecycle phases

Understandable content NFRs are defined during requirements, workflow design, and content design; implemented during UI development; validated during accessibility, usability, and UAT testing; and improved through analytics and support trends.

Best Practice: Define robust markup, semantic structure, and assistive technology compatibility non-functional requirements

Description

Robust implementation NFRs define how software structure, markup, roles, states, names, headings, landmarks, and interaction patterns can be interpreted reliably by browsers, assistive technologies, automation tools, and future user agents.

Benefits

Robust implementation improves accessibility, maintainability, testability, automation reliability, and compatibility across tools and devices.

Example non-functional requirements

• All primary pages shall use a logical heading hierarchy, semantic landmarks, and accessible names for interactive controls.

• Validation method: Validate through markup inspection, automated accessibility scan, screen reader navigation test, and code review.

• Example validation evidence: Markup review checklist, scan report, screen reader navigation evidence, code review record, and accessibility signoff.

• Custom UI components shall expose correct roles, states, labels, and keyboard behavior consistent with approved accessibility patterns.

• Validation method: Validate through component-level accessibility testing, design-system review, assistive technology testing, and regression testing.

• Example validation evidence: Component accessibility test report, design-system approval, screen reader test notes, regression test results, and defect closure record.

Related stakeholders

Typical stakeholders include front-end developers, design-system teams, accessibility specialists, QA automation teams, UX designers, and product owners.

Related lifecycle phases

Robust implementation NFRs are defined during architecture and design-system planning; implemented during component development; validated through code review, accessibility testing, and regression testing; and maintained through component library governance.

Best Practice: Define screen reader and assistive technology test-coverage non-functional requirements

Description

Assistive technology test-coverage NFRs define which assistive technologies, browsers, operating systems, user roles, and workflows must be included in accessibility validation. They should prevent overreliance on automated scans alone.

Benefits

Explicit test coverage improves release confidence, reveals real interaction defects, and supports defensible accessibility evidence.

Example non-functional requirements

• Accessibility validation shall include manual testing of critical workflows with at least one approved screen reader and supported browser combination.

• Validation method: Validate through test plan review, manual test execution, workflow coverage analysis, and defect review.

• Example validation evidence: Assistive technology test matrix, manual test notes, workflow coverage report, defect log, and approval record.

• Critical keyboard and screen reader defects shall be remediated or formally risk-accepted before production release.

• Validation method: Validate through defect triage review, remediation retest, exception approval review, and release-readiness checkpoint.

• Example validation evidence: Accessibility defect report, retest evidence, approved exception record, release checklist, and signoff.

Related stakeholders

Typical stakeholders include accessibility specialists, QA teams, UX teams, developers, product owners, legal/compliance stakeholders, and representative assistive technology users.

Related lifecycle phases

Assistive technology coverage NFRs are defined during test planning; validated during accessibility testing and UAT; and revisited when supported browsers, devices, content, or assistive technologies change.

Best Practice: Define caption, transcript, audio description, color, contrast, and visual presentation non-functional requirements

Description

Media and visual presentation NFRs define how non-text content, video, audio, color usage, contrast, typography, spacing, and visual cues must be accessible and understandable.

Benefits

These requirements improve inclusion for users with auditory, visual, cognitive, or situational limitations and reduce risk from inaccessible media or visual-only communication.

Example non-functional requirements

• All prerecorded training videos embedded in the application shall include accurate captions and transcripts before publication.

• Validation method: Validate through media review, caption timing inspection, transcript verification, and content owner approval.

• Example validation evidence: Caption file, transcript, media review checklist, timing verification record, and content approval.

• Status, warning, and error information shall not rely on color alone and shall include text, iconography, or accessible labels.

• Validation method: Validate through visual review, accessibility inspection, screen reader testing, and design-system review.

• Example validation evidence: Visual review checklist, accessibility scan output, screen reader test notes, design-system approval, and defect closure evidence.

Related stakeholders

Typical stakeholders include content owners, UX designers, accessibility specialists, training teams, developers, QA teams, and product owners.

Related lifecycle phases

Media and visual presentation NFRs are defined during content and design planning; implemented during UI and content development; validated during accessibility review; and maintained through content governance.

Best Practice: Define accessibility exception, remediation, and release-readiness non-functional requirements

Description

Accessibility exception and remediation NFRs define how accessibility defects, unresolved issues, release risks, waivers, remediation commitments, and approvals must be handled. They should distinguish acceptable temporary exceptions from defects that block release.

Benefits

Exception and remediation requirements ensure that accessibility defects are visible, governed, risk-assessed, and remediated instead of silently deferred.

Example non-functional requirements

• No critical accessibility defect affecting a legally required or business-critical workflow shall be released without an approved exception, remediation plan, and target date.

• Validation method: Validate through defect triage review, exception record inspection, remediation plan review, and release approval checkpoint.

• Example validation evidence: Accessibility defect log, approved exception record, remediation plan, release-readiness signoff, and follow-up tracking record.

• Accessibility exceptions shall identify affected users, affected workflows, business impact, risk owner, mitigation, and remediation date.

• Validation method: Validate through exception template review, governance approval review, and periodic remediation status review.

• Example validation evidence: Exception form, risk owner approval, mitigation record, remediation backlog item, and status report.

Related stakeholders

Typical stakeholders include product owners, accessibility specialists, legal/compliance stakeholders, release managers, QA teams, support teams, and business owners.

Related lifecycle phases

Exception and remediation NFRs are defined during governance and release planning; validated during release readiness; and tracked through remediation, maintenance, and audit review.

Best Practice: Define accessibility validation and evidence non-functional requirements

Description

Accessibility validation and evidence NFRs define the test methods, evidence artifacts, approvals, and records required to prove accessibility requirements have been evaluated and satisfied.

Benefits

Clear evidence expectations make accessibility review repeatable, auditable, and easier to sustain across releases.

Example non-functional requirements

• Each major release shall retain accessibility validation evidence for in-scope user-facing workflows.

• Validation method: Validate through release evidence review, test artifact inspection, defect closure review, and accessibility signoff.

• Example validation evidence: Accessibility validation package, scan reports, manual test notes, defect closure report, exception log, and approval record.

• Accessibility regression testing shall be performed for reusable components and templates before they are promoted to the shared design system.

• Validation method: Validate through component regression test execution, design-system governance review, and release approval.

• Example validation evidence: Component test report, design-system review notes, regression evidence, approval record, and version history.

Related stakeholders

Typical stakeholders include accessibility specialists, QA teams, UX teams, developers, design-system teams, product owners, release managers, and compliance stakeholders.

Related lifecycle phases

Accessibility validation NFRs are defined during test planning and governance; validated before release; and retained for audit, compliance, improvement, and future regression testing.