Defines inclusive behavior, semantic requirements, assistive-technology expectations, and common failure cases for semantic HTML. It fixes adoption boundaries and observable failure evidence while keeping environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Semantic HTML, adopt native semantics first, with a documented keyboard and focus contract. Specify semantic, keyboard, focus, announcement, visual, motion, and error behavior as part of the component's functional contract. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Semantic HTML actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes described by this accessibility block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Expose a programmatic name, role, value, state, and relationship wherever the visual interface communicates them.
- Every action is operable by keyboard without a trap, and focus order follows the reading and interaction order.
- Announce asynchronous status or errors without moving focus unexpectedly, and associate recovery guidance with the affected control.
- Preserve content and operation under zoom, text spacing, reflow, forced colors, reduced motion, and platform text scaling where applicable.
- Prefer native elements; when a custom widget is necessary, implement its complete expected interaction pattern rather than only adding a role.
- Test with multiple input modes and at least one representative screen-reader/browser combination defined by the adopting team.
- Use the native element whose semantics match the interaction and preserve heading hierarchy, landmarks, lists, tables, labels, descriptions, and document order before adding ARIA.
- Validate the accessibility tree and keyboard behavior after client rendering and do not use roles to repair an element whose native behavior has been broken by scripting.
Implementation guidance
- Write the keyboard and focus sequence before implementation and review copy with visible labels and programmatic names side by side.
- Model Semantic HTML inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Semantic HTML contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- If semantics or focus cannot be preserved, the interaction does not ship behind visual-only behavior; the defect remains release-blocking.
- Invalid or contradictory Semantic HTML state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Verify automated rules, keyboard-only operation, focus visibility, announcements, contrast, zoom, and manual task completion.
- Monitor Semantic HTML success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.