Built element and distribution occurrence classes.
A type definition says what a pump is; an occurrence says that one particular pump sits here, in this system, with this tag. This crate authors the occurrence side and enforces the link between the two: the schema pairs each occurrence class with exactly one type class, and a mismatch is refused rather than written.
The catalogue in [table] is generated from
references/ifc-spec/ifc4x3-add2/IFC4X3_ADD2.exp by
scripts/gen-occurrences.py; [create] is the writer.