universal_automation_semantics 0.4.0

The semantic view grammar for the universal automation family: declarative views over accessibility snapshots, ref-stable observations, observation diffs, and compact text rendering. Pure Dart, no Flu [...]

universal_automation_semantics

The semantic view grammar for the universal automation family (ADR 0052): what an agent's observe/act loop actually reads. Pure Dart over the family Snapshot — no Flutter, no protocol clients. Every tier projects its native tree (Flutter semantics, macOS AX, AT-SPI, UIA, CDP a11y) into AxNodes and shares this layer, so refs, diffs, and renders mean the same thing everywhere.

The layered composition API

One layer per concern, all of them values — the same decomposition Flutter uses, one level up:

Layer	Type	Composition
Declaration	SemanticView	const-built, nested (panes), builder-refinable
Instance	Observation	Observation.of(snapshot, view) — refs issued, selection applied
Read-out	render() / diff()	text and JSON, managed here

Both construction directions work everywhere — declare a whole tree in one expression, or refine iteratively; call a single terminal observation, or compose views into step trees (in the toolkit: observe(view: …), act(..., returnState: true), scope(view, [...])).

// Declarative: one const tree, panes nesting views nesting views.
const view = SemanticView(
  maxNodes: 200,
  panes: {'toolbar': SemanticView(subtreeOf: 's_1')},
);

// Iterative: builder refinement of the same value.
final tuned = view.trimmed(50).withPane('list', SemanticView(maxNodes: 40));

// Terminal: one observation, one call.
final observation = Observation.of(await driver.snapshot(), tuned);
final text = observation.render();   // numbered compact text
final delta = observation.diff(last); // +/-/~ rows with stable refs
observation.resolve('s_3');           // fail-closed ref resolution

Invariants

1. Refs number the full walk in document order (s_N; each pane renumbers its own subtree as <pane>.s_N). Views, filters, and trimming decide what is shown, never what is numbered — a ref read off a filtered or trimmed observation stays valid.
2. Resolution is not display: every walked ref resolves; a ref no walk issued fails closed with SemanticRefUnavailableException (reobserve, never guess).
3. Diffs match by structural signature, so reflows report no change and value changes report as ~ rows carrying the new refs.

Wire form

SemanticView.toJson()/fromJson() speak mcp_flutter's semantic_snapshot filter keys (identifierPrefix/subtreeOf/ fields) plus family extensions (maxNodes, panes) — the same keys work in plan documents and MCP automation_observe arguments.

{"subtreeOf": "s_1", "fields": ["role", "name", "value"], "maxNodes": 120,
 "panes": {"header": {"maxNodes": 5}}}

Producers: projecting a native walk (ADR 0052 full cutover)

A producer's walk stays native; this package owns everything after the tree exists. For tiers that emit Flutter-shaped node maps (type/label/value/bounds, children as ref lists — mcp_flutter's semantic_snapshot today):

• snapshotRef(i) — the one ref dialect (s_N, document order);
• familySnapshotFromNodes(nodes, snapshotId:, capturedAt:) — the projection into the family Snapshot (role/name/value/bounds on the shared axis, the producer's vocabulary in attributes);
• projectSnapshotNodes(nodes, keep:, fields:) — the envelope-side selection policy (fields projection with ref always kept, children pruned to kept refs, emptied children dropped).

final observation = Observation.of(
  familySnapshotFromNodes(emitted, snapshotId: id, capturedAt: now),
  view,
);

Grounding: nodeAt (ADR 0053)

observation.nodeAt(x, y) answers "which element is at this point" from the tree's own bounds — the walked node containing the point, smallest area first (innermost wins), fail-closed with SemanticRefUnavailableException when nothing covers it. Bounds grounding needs no screenshots; pixel grounding stays client-side.