Crate ifc_schema 

ifc-schema — the IFC schema as data, not as 2,500 generated structs.

The decision

IfcOpenShell generates a class per IFC entity per schema version. That is a very large amount of code, and it must be regenerated for every schema release. This crate instead reads the normative EXPRESS files into tables and answers questions against them.

The evidence that this is the right call: IFC4x3 renames IfcBuildingElement to IfcBuiltElement and drops IfcProxy and the whole *StandardCase family. Generated types would fork the entire API surface; a table just holds different rows.

What this crate is for

Module	Role
version	Which schema a file declares
express	Parsing .exp source (opt-in express feature)
entity	Entity descriptors: name, supertype, slots
attribute	Attribute descriptors and declared types
types	Defined types, enumerations, selects
registry	The assembled, queryable schema

Relationship to the model

ifc-model does not depend on this crate. The model stores whatever a file contains, valid or not. The schema is what you consult to interpret what was stored, and it is optional: a file whose schema is unknown still parses, and its entities still round-trip.

Features

Feature	Default	Provides
ifc2x3, ifc4, ifc4x1, ifc4x2, ifc4x3	yes	That release’s bundled table and accessor (ifc2x3(), …)
artifact	via any release	The compiled-artifact decoder
express	no	Schema::from_express through openbim-step
generation	no	The artifact generator binary

A default build bundles every release. A build that turns defaults off and names one release still recognises every SchemaVersion, and for_version refuses the others with NotBundled – a typed error, never a panic, and distinct from an unknown header token.

Owned declaration types

EntityDef, Attribute, TypeDef, TypeKind and WhereRule belong to this crate and are #[non_exhaustive]. The bundled tables decode straight into them without any parser crate; the openbim-step EXPRESS extractor is linked only by the opt-in express feature (for Schema::from_express) and by generation.

let schema = ifc_schema::ifc4();
assert!(schema.is_a("IFCWALL", "IfcRoot"));
assert_eq!(
    &schema.attribute_names("IfcWall")[..2],
    ["GlobalId", "OwnerHistory"]
);

Re-exports

pub use attribute::AggregateKind;

pub use attribute::Aggregation;

pub use attribute::Attribute;

pub use attribute::Bound;

pub use entity::EntityDef;

pub use entity::InverseAttribute;

pub use entity::UniqueRule;

pub use entity::WhereRule;

pub use export::write_direct_structural_catalog;

pub use export::write_structural_catalog;

pub use export::StructuralCatalogSummary;

pub use registry::Schema;

pub use types::TypeDef;

pub use types::TypeKind;

pub use version::SchemaVersion;

Modules

attribute

One positional attribute slot on an IFC entity, and aggregate shapes.

completeness

Prove a hand-written entity inventory is complete against the normative EXPRESS schema.

entity

Entity descriptors used by the IFC schema registry.

export

Deterministic, schema-derived structural catalog export.

registry

The assembled, queryable IFC schema.

types

Defined types, enumerations, and selects used by IFC schemas.

version

Which IFC schema version a file declares.

Structs

NotBundled

A recognised IFC release whose table is not compiled into this build.

Enums

BundledSchemaError

Failure decoding a compiled schema artifact.

Functions

artifact_decode_schema

Decodes a compiled schema artifact produced by encode_schema (the generation feature).

for_version

The bundled schema for version.

ifc4

The bundled IFC4 ADD2 TC1 schema (776 entities, 397 types).

ifc2x3

The bundled IFC2x3 TC1 schema (653 entities, 327 types).

ifc4x1

The bundled IFC4X1 FINAL schema (801 entities, 400 types).

ifc4x2

The bundled IFC4X2 FINAL schema (816 entities, 407 types).

ifc4x3

The bundled IFC4X3 ADD2 schema (876 entities, 436 types).