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13 — Semantics, accessibility and behavior

Document status: exploratory draft. Canonical source.

Semantic role layer

NUIF entities MAY carry semantic roles independently of visual entity kind. The current wire model carries a portable role identifier, one direct accessible name and Boolean state keys. Document relationships can express labelled-by, described-by, controls, owns and flow-to. A direct description string, non-Boolean value/state data and semantic relationship cardinality rules require a future schema revision; adapters MUST NOT invent them from visual geometry.

Adapters MUST map portable semantics to host accessibility facilities where supported and MUST report unsupported or approximated semantics. Visual appearance MUST NOT be treated as sufficient evidence of semantic role.

Web accessibility projection profile 0

nuif-web-accessibility-0 is an experimental bounded lowering to inert HTML and ARIA. It admits at most 4,096 entities and 8,192 relationships. Its role set is button, checkbox, group, img, main, navigation, paragraph, radio, region and switch. Role-specific required/prohibited naming and Boolean-state rules are fixed by the profile. A switch MUST carry checked; unsupported or misplaced states MUST fail closed. A direct accessible name and labelled-by MUST NOT compete on one entity. Direct and referenced names MUST be whitespace-normalized for computed-name comparison and MUST NOT be empty after normalization.

The five relationship kinds above lower to their corresponding ARIA IDREF attributes using stable NUIF entity identifiers. Relationship order is retained and duplicate targets fail closed. The owns graph MUST be acyclic and each owned target MUST have at most one ARIA owner. Native HTML semantics are used where the profile has an exact element; explicit ARIA is used only for group, img and switch. Output contains no script, external URL, event handler or synthesized host behavior.

The foreign oracle MUST record the exact test-engine and host versions, compare computed role/name/state rather than source attributes alone and classify required-subset loss separately from other host-tree differences. Browser-tree agreement does not establish native platform API, keyboard interaction or application behavior equivalence.

Behavior graph

Portable interaction is represented as a separate bounded graph referencing stable entity/property identities. It MUST NOT embed arbitrary general-purpose code. The initial executable research profile is deliberately smaller than the eventual vocabulary of events, state, value transforms, property writes, navigation and animation triggers.

Behavior capabilities are negotiated like extensions. Missing optional capabilities may degrade according to declared fallback; missing required capabilities prevent a claim of behavioral conformance.

Behavior state-machine profile 0

nuif-behavior-state-machine-0 is an experimental sidecar and is not part of the canonical semantic Document model. It defines a flat deterministic state machine with a single active state. Its only external event is activate, addressed to a stable entity carrying role button, checkbox, radio or switch. Transitions in the active state are evaluated in authored order; the first exact event and equality-guard match executes its actions sequentially and selects its target state. An unmatched event is a no-op. An event MUST complete before the next external event is accepted.

Profile values are Boolean or bounded string. Actions may set a value, toggle a Boolean or emit an abstract visibility(Boolean) or announcement(String) effect to a stable entity. The reference runtime MUST NOT directly mutate the document or invoke host APIs. Target adapters consume effects under separately declared capability and fidelity contracts.

Every used effect capability MUST be declared required or optional_noop. A missing required capability MUST reject runtime construction before actions execute. An unavailable optional capability MUST emit no host effect and MUST be recorded as skipped in the trace. Unknown or incompatible entities, states, variables, value types, capabilities, unreachable states and over-limit graphs MUST fail closed before execution.

The profile admits at most 128 states, 1,024 transitions, 4,096 total actions, 64 actions per transition, 128 variables, 64 capabilities and 4,096 external events per run. Timers, internal events, parallel states, numeric computation, navigation, animation, filesystem/network effects and scripts are excluded. Conformance compares complete event, selected-transition, state, variable, effect and skipped-capability traces. Final-state agreement alone is insufficient.

Behavior package resource profile 0

nuif-behavior-package-resource-0 is the experimental transport defined by RFC 0012. It does not change nuif-package-0 or the canonical Document. Exactly one embedded resource MAY carry a behavior program. Its descriptor MUST use role source, no derivation and provisional media type application/nuif-behavior+cbor; its bytes MUST be canonical nuif-cbor-0 for one nuif-behavior-state-machine-0 program. The package manifest MUST also declare nuif-behavior-state-machine-0 as a required capability.

A behavior capability without its resource, a behavior resource without its capability, multiple behavior resources, a linked resource, non-canonical bytes or a program invalid for the package document MUST fail the attachment profile. The program MUST validate against the actual package document both before attachment and after decode.

The resource digest identifies exact behavior bytes; it does not include the document hash. The deterministic package manifest and complete package hash bind the behavior descriptor and document descriptor together. Attachment therefore changes the package hash without changing the semantic document hash. A transplanted resource MUST be revalidated against its new package document.

Generic package decoding MAY verify, preserve and re-encode the inert resource without interpreting it. Full behavioral conformance requires explicit attachment decoding and a separately authorized runtime capability set. Opening, inspecting or preserving a package MUST NOT execute behavior or grant filesystem, network, script or host-mutation authority.

Web behavior projection profile 0

nuif-web-behavior-0 is an experimental one-way composition of nuif-behavior-state-machine-0 and nuif-web-accessibility-0. The complete source profiles MUST validate before host output. The web projection admits activate only for enabled native button elements or the button-backed switch role. Checkbox and radio event sources and disabled transition sources MUST fail closed. Every enabled button/switch in the document MUST be bound so an activation with no matching transition retains the source profile’s no-op semantics. A visibility effect MUST NOT hide an admitted event source or its containing ancestor because later native activation would become impossible.

visibility(Boolean) MUST map to the target HTML element’s hidden property. A non-empty announcement(String) MUST map to the text of one unfocused status live region with polite, atomic semantics and retain its stable target identity as observation metadata. A transition MUST NOT emit more than one announcement or repeat the same effect-kind/target pair because a single host task may collapse those abstract effects into one observation.

The generated output MUST contain only a fixed finite interpreter plus the validated program as escaped data. Program strings MUST NOT terminate the script element. Arbitrary authored script, handler attributes, evaluation, dynamic import, timers, network and filesystem authority are prohibited. A self-contained document MUST restrict the exact runtime by a content hash and deny every unneeded resource class. A serving host SHOULD deliver its own response-header Content Security Policy and MUST NOT assume a nested document’s policy transfers to the host page.

Conformance MUST drive native activation and compare selected transition, target state and retained host effects after every event through each declared engine. DOM and browser accessibility-tree observations do not establish assistive-technology speech, focus behavior or native platform UI equivalence.

Host logic boundary

Application business logic, arbitrary network effects and unrestricted scripts are outside the core document model. Adapters may preserve references/bindings to host logic using extensions and provenance, but another implementation is not required to execute unknown host code. The state-machine sidecar MUST NOT be interpreted as authority to execute such bindings.

Inference

Behavior inferred from screenshots or static design states is never lossless solely because the generated result looks equivalent. Inference records MUST identify evidence, confidence and unresolved alternatives.