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- §4.1 Language honesty: every language states how its core vocabulary was obtained (CoreStatus); an absent status reads as GlossOnly; glosses are never presented as a language's core. Withdraws the claim that one ~400-word core covers ~80% of every language. - §5.1 Timing belongs to the person: scan rate and dwell are theirs to set; automatic adaptation is off unless they opt in; changes are proposed, never silent. - §5.2 Scan-rate floor: max(⌊100·M/65⌋, P95), from at least 10 responses. The previous reference set 80% of the mean press, so the highlight had usually moved on when the person pressed. - §5.3 Dwell proposals go both ways, with floors, replacing "should adapt to fatigue" (the old reference only ever lengthened the dwell). - §10 adds C5–C7; §11 says access and vocabulary choices are never a prerequisite for starting. - spec/access_model.md, the lexicon and the ontology agree (new CoreStatus class and individuals; scanRateMs, dwellMs, adaptationOptIn; Turtle, SHACL and JSON-LD validated with rdflib). New aac-rs/README.md covers testing, the static build, and hosting Express under another site. Co-Authored-By: Claude Opus 5.5 <[email protected]>
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AAC sub-spec — The access model
Normative refinement of SPEC §5. Reference: aac_core::{AccessMethod, MotorProfile, ScanConfig, ScanMode, DwellConfig}.
Every access method is a first-class input. The method and its tuning travel with the user, not the board: a board authored for eye-gaze MUST still open under touch or a switch (SPEC §5.3).
1. Access method — AccessMethod
DirectTouch (default) · EyeGaze · HeadTracking · SwitchScan { switches: u8 } · Joystick · Bci · PartialVoice · Pointer. SwitchScan carries the number of switches available (1, 2, or more); a 1-switch user relies on auto-scan timing, a 2-switch user steps and selects manually.
2. Motor profile — MotorProfile
The user's physical capabilities, used to adapt targets and timing: fine_motor and sustained_press (Full | Limited | None), tremor_level (None | Mild | Moderate | Severe), min_target_mm: f32, optional max_reach_mm, and preferred_side. A client SHOULD derive target size and dwell/scan timing from this profile and MUST NOT render a target smaller than min_target_mm.
3. Switch scanning — ScanConfig
A conforming scanner MUST support at minimum the Linear, RowColumn, and Group modes of ScanMode (also defined: Block, and inverse scanning). It MUST honor:
scan_rate_ms— highlight dwell per step;start_delay_ms— delay before auto-scan begins after a press;max_cycles— complete cycles before stopping (0= infinite);auto_restart— whether scanning restarts after a selection.
scan_rate_ms is the person's to set (SPEC §5.1). adaptive_rate MUST default to false. A rate recommended, proposed or applied from measured responses MUST follow SPEC §5.2: at least 10 recorded responses, at least max(⌊100·M/65⌋, P95) of their response times, clamped to [300, 5000] ms. Without opt-in the scanner MAY only propose that rate (proposed_scan_rate_ms, which offers nothing within 10% of the current rate); with opt-in it MAY apply it. A client that measures responses MUST time them from the moment a highlight appears to the press.
4. Dwell / eye-gaze — DwellConfig
Gaze selection MUST use a configurable dwell time (base_dwell_ms, with the dwell in force in effective_dwell_ms) with visible progress feedback (DwellFeedback) and a tolerance_px radius within which gaze may wander without resetting. A selection MUST NOT fire before the effective dwell elapses.
The dwell is the person's to set (SPEC §5.1; the reference's set_dwell_ms, clamped to [150, max_dwell_ms]). fatigue_adaptation — the reference's name for automatic dwell adjustment — MUST default to false. Proposals (proposed_dwell_ms) follow SPEC §5.3: one ladder step longer when more than 20% of recent selections were undone; one step shorter when fewer than 5% were undone and more than 20% of attempts were abandoned late (gaze left after at least half the dwell); never from fewer than 10 selections, never shorter than 300 ms. A client counts an undo when the person removes a word within a few seconds of selecting it by dwell. The dwell engine reads a monotonic clock that MUST work on the client's platform (the reference uses web-time, since std::time::Instant panics in browsers).
5. Universality
No access method MAY be a precondition for opening or reading a board (SPEC §5, item 3). Choosing an access method is best done by the person with their team, and it is never a prerequisite for starting (SPEC §11); the standard guarantees that whichever method is chosen is a first-class, fully-specified input — never a bolt-on. A client SHOULD start the chosen method as soon as it is chosen (scanning over the board on screen, the camera for gaze) and stop what it no longer needs — in particular, release the camera when gaze is no longer in use.