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This software is OSI Certified Open Source Software. OSI Certified is a certification mark of the Open Source Initiative.


exff is "exPRESS for free"

exff (pronounced "XF") is a project designed to enable the integration and use of the EXPRESS language, and therefore the STEP standards, with UML-based modelling and implementation tools.

The exff Flyer and exff in 10 Minutes may assist in understanding what exff is all about. The Executive Summary and the STEP Summary for the STEP community will also help.

If you are already familiar with exff, then go to the project status pages or the site map. If you are new to exff, then read on.


exff Release 0.1 shows feasibility:

  1. The exff Release 0.1 deliverables allow the use of a UML modeling tool to create and read simple ISO EXPRESS schemas.

The exff Project is currently working/planning Release 0.2. exff will result in a full suite of modelling and implementation tools.


The main exff business goal is to speed the development and deployment of Industrial Data applications.

In the domain of Industrial Data, the ISO EXPRESS data specification language, the eXtensible Markup Language (XML), and the Unified Modeling Language (UML) are three key technologies for the data modeling and software engineering communities.

The exff business goal is to be met by:

  1. enabling the re-use of models across many domains, and
  2. enabling the use of a variety of modeling and implementation systems across the Industrial Data and traditional software engineering communities.


The exff technical approach is to extend existing open source, or free, modeling tools and integrated development environments so that they support the interoperability of the key information technologies. Many of these support the Object Management Group standard for model interchange called XML Metadata Interchange (XMI). XMI is the key enabling technology standard for exff.

By using XMI, the exff results will also be easy to apply to the numerous commercial software tools supporting that standard. This benefits organizations, both large and small, requiring interoperability and allows quicker development and deployment of innovative solutions. Figure 1 shows the architecture of exff. exff allows the interchange between EXPRESS, UML and Integrated Development Environment tools as well as directly driving some aspects of implementation itself.

The exff Architecture Details

Figure 1 - The exff Architecture

The exff infrastructure will also make existing standard models available to a wider audience by allowing them to be recast into the languages used in other disciplines. Examples of this include:

  • logic languages for the Semantic Web,
  • EXPRESS for ISO data exchange protocols,
  • UML and many programming languages for software engineering,
  • SQL DDL for automated generation of relational databases and APIs,
  • XML-based languages for Web Services.

Based on the exff infrastructure, domain-specific applications (e.g. Systems Engineering ) can be developed that implement ISO and OMG standards, and that can be harmonized with related standards and/or proprietary solutions in other domains as well.

Based on the exff infrastructure, organizations will also be able to re-use elements of models, standard or not, in their internal development. This will reduce costs and speed implementation.


The exff Project is developed under the Common Public License.