IFC Core : Data Model and Schema Architecture

The IFC schema is one large EXPRESS model split into many named sub-schemas, each assigned to exactly one of four conceptual layers. The layering and its downward-only referencing rule are the load-bearing structure of the entire standard. Get the layer of an entity wrong, or reference upward, and the model is invalid IFC.

Quick Reference

The model in one sentence

IFC is a single canonical data model written once in the EXPRESS language (ISO 10303-11), organized into four conceptual layers, and serialized into derived encodings (.ifc, .ifcXML, .ifcJSON).

The four conceptual layers