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Welcome to Ratio's Computer Aided Systems Engineering (CASE) knowledge base! We hope you will find what you seek.

This place is the home of:

  • Our best practices and usage of our open-source tools in the field of Systems Engineering such as the use of the Dependency Structure Matrix (DSM).
  • The Elephant Specification Language (ESL), a formal though human-readable language to write system specifications that kick-off your Model-Based Systems Engineering efforts right from the start!

We offer that information in the following formats:

  • Tutorials for a step-by-step approach to learn ESL,
  • How-to guides for a more use-case centric approach,
  • Explanation for more background information regarding systems engineering and engineering design, as well as reasoning behind our methods and tools,
  • Reference for the complete language reference and nitty gritty,
  • Governance for the language enhancement proposals and their current status.


This page aims to replace in due time. We're currently in the process of transferring all content, so some pages might be incomplete.


Looking for Python package docs? Head over to the specific websites for RaGraph and RaESL.


If you're looking to code and contribute, you might want to check out our repositories over at our GitLab organization. There are Visual Studio Code (or Codium) extensions, Python packages, Rust crates, Docker images (i.e. for JupyterHub), some general development helpers, and of course the source code for this guide.

Who is Ratio CASE?

OK, but who or what is Ratio? We're a company founded by Tim Wilschut and Tiemen Schuijbroek and are based in Eindhoven, the Netherlands. The home of companies like ASML, Philips, and our alma mater: The Eindhoven University of Technology. In short:


Ratio CASE focuses on the development of methods and tools for the specification, visualization, analysis, and optimization of system architectures to support engineers in avoiding rework and in developing even better systems. Ratio combines the latest innovative and scientific insights as well as algorithms to ultimately boost the productivity of our clients and their partners.

Could use some help?

Are you looking for help in the field of systems engineering? Would you like some training for yourself or your employees? We, Ratio Computer Aided Systems Engineering or Ratio CASE if you will, are here to help! Head over to our main website and look for our contact options. We offer:

  • Systems modelling and analysis workshops
  • Elephant Specification Language training
  • Systems Engineering support
  • Systems Engineering consultancy services

We've got more than 4 years of experience as a company in brownfield analysis of system architectures and requirements analysis. It might actually be 8 if you count Tim's 4-year PhD in the field of Systems Engineering at the Eindhoven University of Technology for the Dutch Ministry of Infrastructure. Through our structured approach we offer our customers:

  • A start with Model-Based Systems Engineering right from their requirements!
  • Gain valuable insights and deep understanding into their current products' architecture by analyzing current documentation.
  • Are enabled to develop product platforms to move from an Engineer-to-Order to a Configure-to-Order approach.


All our open-source software can be found over at our GitLab organization.

All software related to the processing of the Elephant Specification Language (ESL) is MIT or Apache-2.0 licensed at your volition, since we believe a language is as good as the people that can use it unconstrained!

All our analysis software in the field graph (network) or Dependency Structure Matrix analysis is licensed under the GPL-v3.0-or-later license, since we believe in encouraging companies to distribute their packages as open-source for these more "exploitation" oriented packages. For tailor-made licensing options, for instance for incorporation of any of our packages into commercial software where the GPL license is not feasible, please reach out to us via the contact options on