ifc-schema 0.2.1

IFC schema as data: entity table, supertype chain, attribute names.
Documentation

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] Parser for the official .exp files
[entity] Entity descriptors: name, supertype, slots
[attribute] Attribute descriptors and declared types
[types] Defined types, enumerations, selects
[registry] The assembled, queryable schema
inheritance Supertype-chain walking

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.

use ifc_schema::Schema;

let schema = Schema::from_express(
    "SCHEMA IFC4;\n\
     ENTITY IfcRoot; GlobalId : IfcGloballyUniqueId; END_ENTITY;\n\
     ENTITY IfcWall SUBTYPE OF (IfcRoot); Name : IfcLabel; END_ENTITY;\n\
     END_SCHEMA;",
);

assert!(schema.is_a("IFCWALL", "IfcRoot"));
assert_eq!(schema.attribute_names("IfcWall"), ["GlobalId", "Name"]);