The EXPRESS Language Family

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

EXPRESS-Q

ELF Specification

Query language for defining mappings between Application Reference Model (ARM) and Model Implementation Model (MIM) schemas, with reference path syntax for precise schema navigation.

Developed alongside EXPRESS-X for ARM-to-MIM schema mapping.

• ENTITY_MAPPING declarations
• ATTRIBUTE_MAPPING definitions
• Reference path syntax
• EXPRESS links
• YAML serialization