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EXPRESSLanguage Foundation
EXPRESS-G

EXPRESS-G

ISO 10303-11:2004

Overview

EXPRESS-G is the graphical notation for the EXPRESS information modelling language. It provides an entity-relationship style diagram syntax for visual representation, communication, and documentation of EXPRESS data models.

EXPRESS-G mirrors a subset of the EXPRESS lexical syntax, offering a visual alternative that is particularly useful for: presenting model overviews to stakeholders, documenting schema structures, and facilitating collaborative design sessions.

Key features

  • Entity type symbols — rectangular boxes representing entities with their attributes

  • Relationship lines — directed arcs showing attribute references and associations

  • Subtype/supertype diagrams — visualization of inheritance hierarchies

  • Attribute annotations — optional/mandatory indicators, cardinality

  • Schema diagrams — page-level organization showing schema boundaries

  • Defined type representations — visual encodings for ENUMERATION, SELECT, and user-defined types

Notation

EXPRESS-G uses a simple but powerful visual vocabulary:

  • Rectangles — entity types and defined types

  • Rounded rectangles — schema symbols

  • Lines with arrows — relationships (attributes, references)

  • Thick lines — subtype/supertype relationships

  • Dashed lines — optional attributes

  • Circle markers — cardinality indicators

The notation supports two levels of detail: compact notation (entities with attribute names only) and full notation (entities with complete attribute type information).

History

EXPRESS-G was designed by Peter Wilson as a companion graphical notation to the EXPRESS language. It was developed alongside EXPRESS during the standardization process at ISO, becoming part of the same standard (ISO 10303-11).

Timeline

1980s

EXPRESS-G developed by Peter Wilson as a visual companion to EXPRESS

1994

Published as part of ISO 10303-11:1994 (EXPRESS language standard, Annex A)

2004

Updated in ISO 10303-11:2004 (Edition 2)

Key people

Peter Wilson

Designer of EXPRESS-G and co-designer of the EXPRESS language. Author of the authoritative EXPRESS reference manual with Douglas Schenck.

Standardization

EXPRESS-G is defined in Annex A of ISO 10303-11 (same standard as EXPRESS), ensuring perfect alignment between the graphical and lexical forms.

  • ISO 10303-11:1994, Annex A — First formal definition of EXPRESS-G notation

  • ISO 10303-11:2004, Annex A — Updated notation in Edition 2

Tools

Several tools support EXPRESS-G diagram creation and editing:

  • EDMvisualExpress — visual EXPRESS-G diagram editor from Jotne EPM Technology

  • STEPmod — ISO tool for generating EXPRESS-G diagrams from EXPRESS schemas

  • Graphical EXPRESS — various open-source and commercial editors

Learn more