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Expressir (“EXPRESS in Ruby”) is a Ruby parser for EXPRESS and a set of Ruby tools for accessing ISO EXPRESS data models.


Expressir consists of 3 parts:

  1. Parsers. A parser allows Expressir to read EXPRESS files, including:

    • EXPRESS data modelling language (ISO 10303-11:2007)

    • EXPRESS data modelling language in XML (STEPmod)

    • EXPRESS XML (ISO 10303-28:2007) “Industrial automation systems and integration — Product data representation and exchange — Part 28: Implementation methods: XML representations of EXPRESS schemas and data, using XML schemas”)

  2. Data model. The data model (lib/expressir/express) is the Ruby data model that fully represents an EXPRESS data model.

  3. Converters. A converter transforms the EXPRESS Ruby data model into an interoperable export format, including:

    • EXPRESS data modelling language (ISO 10303-11:2007)

    • W3C OWL

    • OMG SysML (XMI 2.1, XMI 2.5)

    • OMG UML 2 (XMI 2.1)

    • OMG UML 2 for Eclipse (XMI 2.1)


This gem ships with a CLI tool. To check what’s available you can simply run the script directly from exe/expressir, by default it will display some usage instructions.


  expressir help [COMMAND]  # Describe available commands or one specific command
  expressir version         # The Expressir Version


We are following Sandi Metz’s Rules for this gem, you can read the description of the rules here All new code should follow these rules. If you make changes in a pre-existing file that violates these rules you should fix the violations as part of your contribution.


Clone the repository.

git clone

Setup your environment.


Run the test suite


Grammar updates

EXPRESS grammar is lined as git submodule to ext/express-grammar Shoudl you update it, run rake generate. This command will generate source code for updated native extension using antlr4-native gem. Please note that we create several classes on top of antlr4-native output so using embedded rake task is a real requirement.

When new extension is gnerated and tested plase check in updated C++ files to git (rake generate is NOT a CI step, extension source files are pulled from the repo).


Add this line to your application’s Gemfile:

gem "expressir"

And then execute:

$ bundle install

Or install it yourself as:

$ gem install expressir


First, thank you for contributing! We love pull requests from everyone. By participating in this project, you hereby grant Ribose Inc. the right to grant or transfer an unlimited number of non exclusive licenses or sub-licenses to third parties, under the copyright covering the contribution to use the contribution by all means.

Here are a few technical guidelines to follow:

  • Open an issues to discuss a new feature.

  • Write tests to support your new feature.

  • Make sure the entire test suite passes locally and on CI.

  • Open a Pull Request.

  • Squash your commits after receiving feedback.

  • Party!


Expressir is distributed under the BSD 2-clause license.

Expressir is built on code originally from the NIST Reeper project.

The NIST Reeper license is reproduced below:

This software was funded by NIST and developed by EuroSTEP. Pursuant to title 17 Section 105 of the United States Code this software is not subject to copyright protection and is in the public domain.

We would appreciate acknowledgment if the software is used. Links to non-Federal Government Web sites do not imply NIST endorsement of any particular product, service, organization, company, information provider, or content.


Expressir is created using the structure and examples provided by the NIST Reeper software on Sourceforge.