Grammar prerequisite · source-authoritative geometry

Geometry Plane and Arc Representation Grammar

A physical cross-section is incomplete without its plane, and a local circle radius is not the tokamak cylindrical radial coordinate merely because both DD leaves are named r. ISN must make those meanings grammatically distinct and round-trippable.

✓ landed 2026-08-10

Required semantic separation

poloidal_plane_cross_section, local_circle_radius_of_passive_loop_element and radial_coordinate_of_passive_loop_element now preserve three distinct identities; ordinal forms remain invalid. Full record: semantic separation (merge b32f6b8).

✓ landed 2026-08-10

Grammar contract

Added closed section-plane and geometry-representation segments, canonical poloidal_plane_ serialization, strict parser/composer constraints, generated public types and grammar-context exposure. The independently verified tree passed 1,993 tests with 33 skipped, 82 expected failures, 2 warnings and 91% total coverage; full verification record.

✓ landed 2026-08-10

Repository boundary

The change is confined to ISN grammar, validation, generated types and public grammar context. DD interpretation, graph membership and promotion/recovery authority remain in imas-codex; boundary evidence.

§ Decisions

Where must section-plane semantics be available?

A cross-section is incomplete unless the plane is part of the identity. The rule applies to hardware and any other carrier for which the section plane changes the physical object represented.

Locked by the lead as 1A: ISN must add the grammar segment, ordering, and vocabulary. The segment is generic; carrier-specific admissibility remains grammar/semantic validation.

May sample order or endpoint position enter the identity?

DD paths may contain first, second, start, or end positions, but those are sampling/provenance details.

Strict project rule: first, second, start, end, and equivalent ordered sample labels remain in DD provenance and never enter the Standard Name.

§ Followups

Add plane-qualified section and local-arc semantics to the public grammar

Add the section-plane segment and arc representation vocabulary to ISN, place the new segment canonically in the grammar, expose it through the public grammar context, and prove strict parse/compose round trips and ambiguity rejection.

/reckon-ship geometry-plane-and-arc-grammar

Landed in b32f6b8: closed plane and local-circle grammar, unambiguous poloidal_plane serialization, public context/codegen and strict semantic gates; 1,993 passed, 33 skipped, 82 expected failures, 2 warnings, 91% coverage.