# AAC lexicon (v1)

The controlled vocabulary of the AAC standard. Terms are stable; their IRIs live in [`v1.ttl`](v1.ttl) under `https://aac.transaction.science/vocab/v1#`.

| Term | Meaning |
|------|---------|
| **Utterance** | The cargo AAC carries: what a non-speaking person means to say, composed by selecting cells. |
| **Board** | A communication surface holding cells, of a given board type. The portable unit a voice travels as. |
| **Board type** | `Grid` \| `VisualScene` \| `Keyboard` \| `Hybrid` \| `QuickAccess`. A rendering + vocabulary-strategy marker. |
| **Cell** | A single selectable target at a fixed grid position, with content and an action. |
| **Position** | `(row, col)`, 0-indexed. Assigned once and **immutable** for the life of the cell — the motor invariant. |
| **Motor stability** | The guarantee that cell positions never move except by explicit edit. Muscle memory is sacred. |
| **Cell content** | `Symbol{id,label}` \| `Text` \| `Photo{ref,label}` \| `Blank`. `Blank` is an addressable reservation of geometry. |
| **Cell action** | What activation does: `Speak` \| `Navigate` \| `Modifier` \| `Backspace` \| `Clear` \| `Predict` \| `SpeakAll` \| `Buffer`. |
| **Symbol** | A pictographic word referenced by source and id — not embedded pixels — so a board stays small and portable. |
| **Access method** | The physical channel of selection: `DirectTouch` \| `EyeGaze` \| `HeadTracking` \| `SwitchScan{n}` \| `Joystick` \| `Bci` \| `PartialVoice` \| `Pointer`. |
| **Motor profile** | The user's physical capabilities (fine motor, sustained press, tremor, target size, reach, side) used to adapt targets and timing. |
| **Scan mode** | The switch-scanning pattern: `Linear` \| `RowColumn` \| `Group` \| `Block` \| inverse. |
| **Dwell** | Eye-gaze selection by sustained gaze, with visible progress feedback and a fatigue-bounded effective time. |
| **Vocabulary level** | `Emergent` \| `Transitional` \| `Conventional` \| `Literate` — the user's stage, which selects the prediction tier. |
| **Cascade** | `L0:Cache → L1:Symbol → L2:LocalPredict → … → L9:AdaptiveModel`. The lowest level that closes a request wins. |
| **Offline invariant** | Exactly L0–L2 are offline-capable and carry 95%+ of communication; a network drop never silences a user. |
| **Free invariant** | No cascade level is gated behind payment at the protocol layer. A voice is not a metered good. |
| **Interchange** | Canonical export + one-directional ingest of existing boards. What goes in comes out; no lock-in. |
| **Receipt** | The per-operation energy record (`measured + estimated` µJ, provenance-tagged) — shown for transparency, **never** billed. |
| **Provenance** | `HwShunt` (hardware-measured) \| `ModelBased` (calibrated model) \| `Estimator` (constant). The honesty tag on every reading. |
| **Steward** | Transaction Science: publishes the spec, ships the reference, runs optional services (symbol libraries, voice banking, team coordination). Not the owner — AAC carries no token. |