Roadmap

Ordered by what unblocks the most downstream work. The roadmap is the curated product narrative; the repository's nested PLAN.md files remain the complete engineering backlog and evidence log. Only tasks promoted to the public Ready for contributors view should be treated as implementation-ready.

Status vocabulary matches the capability matrix. Capability claims below name the implementation or executable evidence that proves them.

Delivered foundations

R0. Declared-schema validation coverage — done, bounded

IFC2X3 TC1, IFC4 ADD2 TC1, and IFC4X3 ADD2 each have independently generated bundled structural tables. validate_declared selects only the file's declared version; all 38 committed fixtures are now audited (31 model-level clean, 7 expected-invalid with observable errors, 0 schema skips). Two raw-header-only defects are normalized by the codec before model validation.

Validation covers structural/reference/type facts plus eight selected native checks represented by nine version-labelled rule IDs. This is not full EXPRESS conformance: aggregate bounds, arbitrary WHERE expressions, INVERSE derivation, and geometry-dependent semantics remain explicitly unsupported and reported.

R1. Typed authoring layer — done

Delivered as ifc-author (facade feature author). Entities are built and edited by attribute name; slot positions come from Schema::attributes. Construction and projected edits refuse unknown entities and attributes, duplicate sets, missing required attributes, declared-type and aggregate mismatches, malformed GlobalIds, and malformed existing arity. Edits stage through ifc-model::Transaction, so dangling references and stale revisions leave the model untouched.

Remaining under AUTHOR in the crate's PLAN.md: a decision on whether IfcOwnerHistory is authored here or injected by an application service.

R2. Relationship and spatial traversal — done

Delivered as ifc-spatial (facade feature spatial), on top of two new ifc-model primitives: ReverseIndex (built on demand, records the attribute slot) and bounded depth_first/breadth_first/find_cycle walks with explicit budgets and cycle reports.

SpatialTree assembles project → site → building → storey → element and tolerates real files: omitted levels, elements on the building, duplicate storeys, dangling references, containment cycles. Defects are reported through orphans() and dangling() instead of being dropped.

Slot layouts are constants rather than schema lookups, because the two relationships that build the tree disagree about slot order and the failure mode is silent inversion. See ADR 0008.

SPATIAL-INV is implemented: callers with repeated inverse lookups build one borrowed RelationshipIndex, which reuses ifc-model::ReverseIndex while preserving tolerant relationship decoding. Grouping implemented ifc-properties views by container remains an L4 orchestration seam.

Presentation and external references

R3. Representation contexts and IfcShapeRepresentation — done

RepresentationContext reads IfcGeometricRepresentationContext and its sub-context: identifier, type, parent, target scale and a typed TargetView (PLAN_VIEW, MODEL_VIEW, ... ; unknown constants preserved rather than flattened). plan_contexts finds the sub-contexts a drawing is authored into.

select_plan_representation is the inverse of select_shape_representation: it prefers a drawable identifier inside an explicit PLAN_VIEW context, then any Plan/Annotation/FootPrint/Axis match, and returns None for a solid-only or box-only product rather than handing back something to draw flat. Context and identifier are intersected: a bounding box in a plan context is still not drawable geometry.

The trap this closes is DERIVED inheritance. A sub-context redeclares six inherited attributes and real files write them as *, meaning "read this from my parent". Accessors taking &model resolve the chain; reading the slot directly yields the marker and loses the project's precision and placement. See ADR 0009.

Not included: authoring helpers for plan sub-contexts (constructible today via EntityBuilder, just without a dedicated builder), and deriving plan geometry from solids — that needs sectioning, tracked as R9b/R10.

R4. ifc-style — presentation appearance

Implemented. Schema-resolved borrowed views cover IfcCurveStyle, IfcFillAreaStyle and its hatch/tile children, IfcSurfaceStyle and its shading/lighting/rendering/refraction children, IfcColourRgb, IfcStyledItem, presentation layers, and the texture family. Selected core style graphs have transaction-staged writers, and style resolution preserves deterministic direct-over-layer precedence.

Remaining boundary. These APIs interpret and author IFC presentation data; they do not render it or compose a drawing.

R5. Annotation entities

Implemented. ifc-style provides strict borrowed views and bounded transaction-staged writers for IfcAnnotation, IfcTextLiteral, IfcTextLiteralWithExtent, and IfcAnnotationFillArea. Annotation type, text path, and box alignment use bounded schema vocabularies.

Note. IFC2x3's IfcDimensionCurve family is correctly absent — it was removed in IFC4. The IFC4 replacement is IfcAnnotation plus ObjectType, property sets, and an Annotation representation context, which makes R3 a prerequisite.

Remaining boundary. Placement, composition, rendering, and general annotation geometry lowering remain application/geometry concerns.

R6. External references and libraries

Implemented. ifc-classification now exposes borrowed IFC4 views for classification systems/references, document information/references, library information/references, all three IfcRelAssociates* families, and the generic IfcExternalReferenceRelationship. Bounded hierarchy lookup reports cycles, dangling/wrong-kind references, and budget exhaustion. Effective classification lookup returns occurrence and type associations separately. Matching transactional helpers author all ten concrete records after validating each draft.

Why it matters. Library references are how a symbol set, a component catalogue, or a classification source stays portable and vendor-neutral rather than proprietary to one application.

Boundary. Approval and constraint resource relationships live in dedicated sibling domains rather than the classification namespace.

R7. Approvals and constraints

Implemented. ifc-approval owns IfcApproval, IfcApprovalRelationship, IfcResourceApprovalRelationship, and IfcRelAssociatesApproval. ifc-constraint owns concrete metrics/objectives, IfcResourceConstraintRelationship, and IfcRelAssociatesConstraint. Both provide strict borrowed views, deterministic direct queries, and typed transaction-staged authoring. A facade/STEP test proves classification, approval, and constraint projections join through stable EntityId values.

Boundary. Approval state is preserved but not treated as authorization, signature, workflow, or policy. Constraints are preserved but not evaluated as compliance rules, formulas, reference paths, tables, or time series.

Geometry coverage

R8. Tessellated face sets — done

IfcTriangulatedFaceSet and IfcPolygonalFaceSet lower through ifc-geometry/src/lower/tessellated.rs into neutral mesh values. Authored triangles, n-gons, and polygonal holes are preserved without inferred topology or forced triangulation. Unit and fixture tests plus the corpus census pin the behaviour; both families are in the dispatcher's IMPLEMENTED table.

R9. Tracked representation-item families — done for the listed set

The formerly planned IfcAdvancedBrep, IfcSweptDiskSolid, IfcSurfaceCurveSweptAreaSolid, IfcSectionedSpine, half-space, and CSG families now appear in ifc-geometry/src/lower/dispatch.rs::IMPLEMENTED and have focused lowering tests. Advanced B-reps preserve shared topology and exact curve/surface handles; half spaces retain their cutting-side semantics; swept and CSG families remain exact neutral operations rather than eager meshes.

Open-profile boundary. IfcArbitraryOpenProfileDef now lowers explicitly through lower_open_profile_node to an authored neutral open path without area or width. Area-profile operations still reject it rather than fabricate a closed contour. Broader exact profile and surface coverage is tracked by GEOM-PROFILE, GEOM-SURFACE, and LOW-EXACT.

R9b. Curve lowering — partial

ifc-geometry/src/lower/curve.rs now emits exact neutral nodes for lines, polylines, circles, trimmed curves, composite curves, and explicit-knot B-splines, including rational weights. The implementation preserves curve parameter units, segment sense, transition codes, closure, and trim selectors; it is exercised directly and through swept-solid fixtures.

Remaining gap. The representation-item dispatcher now lowers the supported curve families as top-level items as well as directrices and members of a geometric collection. Other concrete curve families remain typed Unsupported results. GEOM-CURVE owns completing the family census without approximation.

R10. Plan derivation from 3D

Sectioning solids at a cut height to derive plan geometry. This is a kernel capability, not an IFC one, and no plane-section operation exists in Axiolid at the pinned revision. Tracking it here because applications ask this repository for it; the work itself belongs upstream.

Partial domain slices

ifc-resource now has a tested IFC4/IFC4X3 construction-resource vertical slice: six concrete occurrence kinds, actors (person/organization/role), resource types, inventory, usage quantities, authored resource-time values, allocation lookup, budgeted authored-order composition, and transaction-staged creation of selected records and relationships. IFC2X3 is an explicit typed refusal, not a gap: the schema does not declare IfcConstructionResourceType, IfcResourceTime, or PredefinedType on two occurrence subtypes. It remains partial because scheduling, costing, calendar interpretation, and logistics solving are out of scope.

ifc-georef and ifc-alignment also have tested partial vertical slices: IFC4/IFC4X3 project-to-map/CRS resolution, project-frame composition, and true/grid/project north in the former (rigid coordinate operations and scaled-factor conversion remain refused), and IFC4X3-only exact horizontal line/arc, constant-gradient vertical, full cant-transition, composite-curve assembly, and linear-placement/station-equation output in the latter. ifc-classification, ifc-approval, ifc-constraint, ifc-properties, ifc-style, ifc-structural, ifc-validate, ifc-schedule, ifc-systems, and the bounded ifc-cost contract are implemented; ifc-resource, ifc-geometry, ifc-georef, and ifc-alignment are partial. Each crate's PLAN.md records the remaining scope. Priority among unfinished slices is demand-driven; open an issue describing the use case.

Contributing

Use the public Ready for contributors view rather than choosing an arbitrary unchecked task. Promoted issues name one stable PLAN.md task ID, its current blockers, scope, and required proof. This keeps the detailed backlog in Git while GitHub owns assignment and discussion.

Ideas and unresolved ownership questions, such as the home for approvals, start in repository Discussions. Concrete bugs and feature requests use the issue forms. See the full contributing guide.