ifc-syntax-express
Installation
SKILL.md
IFC Syntax : The EXPRESS Schema Language
Every IFC schema (IFC2x3, IFC4, IFC4.3) is written entirely in EXPRESS, the data modeling language standardized as ISO 10303-11:2004. EXPRESS is declarative : it describes what a valid population of data looks like, never behaviour or algorithms. This skill teaches how to read an EXPRESS declaration and how it maps to a serialized IFC instance. The EXPRESS schema is the single source of truth : the STEP physical file, ifcXML, and ifcJSON are all derived encodings of the same EXPRESS model.
Quick Reference
The three attribute kinds : the most important table
| Kind | Stored? | Serialized in the STEP file? | What it is |
|---|---|---|---|
| Explicit | Yes | Yes : a positional value | An independently stored value, supplied in the file |
| DERIVE | No | No : slot holds * |
A value computed by an expression (:=) |
| INVERSE | No | No : occupies no slot at all | A navigable back-reference, reconstructed by the reader |