Language Family
The EXPRESS Language Family
A family of four complementary information modelling languages for industrial data exchange, smart manufacturing, and interoperability — standardized under ISO 10303.
EXPRESS
ISO 10303-11:2004
The core information modelling language for defining data schemas, entities, types, functions, and constraints. Used across industrial data exchange and product lifecycle management.
Originated in 1982 from the PDDI program at McDonnell Aircraft, invented by Douglas Schenck.
- Entity declarations
- Inheritance hierarchies
- WHERE rules
- FUNCTION / PROCEDURE
- ENUMERATION / SELECT types
EXPRESS-G
ISO 10303-11:2004
Graphical notation for EXPRESS models — entity-relationship style diagrams for visual representation, communication, and documentation of data models.
Designed by Peter Wilson as a visual companion to EXPRESS.
- Entity type symbols
- Relationship lines
- Subtype/supertype
- Attribute annotations
- Schema diagrams
EXPRESS-I
ISO 10303-12
Instance language for defining populated data models and conformance test cases against EXPRESS schemas.
Developed for conformance testing of STEP implementations.
- Instance definitions
- Population data
- Conformance testing
- Validation test cases
- Schema conformance
EXPRESS-X
ISO 10303-14
Schema mapping language for defining transformations between different EXPRESS schemas — supporting 1:1, 1:n, n:1, and n:n cardinalities.
Designed by Peter Wilson for schema interoperability.
- SCHEMA_MAP declarations
- MAP / COMPOSE
- FROM / WHEN clauses
- GLOBAL declarations
- Source-to-target mapping