Welcome to the exff Pages

Goals

The main exff business goal is to speed the development and deployment of Industrial Data applications. The exff Project is an open-source project to provide EXPRESS users with a no cost suite of modeling and implementation tools. The more generic goals are described in the Executive Summary.

The long term goals of the exff project include the following:

1. Broaden the use of EXPRESS and STEP
2. Promote EXPRESS/UML harmonization
3. Promote STEP/OMG domain standards harmonization
4. Enable the publication of "STEP" on the Web

How?

The most important aspect of the approach taken in the exff project is to make a free modelling and implementation environment for EXPRESS available on the Web. There are already several no cost modeling tools that support the Unified Modeling Language (UML). By building on an existing UML graphical tools, a no cost EXPRESS modeling environment can be made available quickly and at a low cost. By simply replacing the use of EXPRESS-G with the use of UML diagrams for data modeling, a vast array of software engineering and data management tools become available.

This exff technical approach is achieved by the following steps.

1. The exff project defines a UML profile for EXPRESS - a profile is a set of constraints applied to the more general UML language.
2. The exff project uses software tool(s) that support the OMG XML Metadata Interchange standard (XMI). Being XMI-driven allows the same technology to be used with commercial UML tools as well. It also allows the use of XML-based tools.
3. The exff project maps the XMI representation of the UML model into the EXPRESS language text format using XML tools.

Why?

The approach taken by the exff project makes sense for several business and technical reasons.

Business benefits

• Widespread - many software developers already use UML tools
• Cost - many UML tools are free (open source) or low cost
• Marketing - EXPRESS/STEP seen as part of a broad, commercial software engineering environment

Technical benefits

First, modelers get the planned EXPRESS 3 capability and more for free! They get:

• Operations on entity data types;
• Conceptual model and implementation model down to the programming level in the same language (OMG MDA);
• State, Use Case, and Activity modelling;
• a richer set of implementation technology bindings (e.g. CORBA, XML, Java, SQL).

This approach also fits into a possible evolution of the relationship between EXPRESS and UML. Efforts have been ongoing for several years attempting to harmonizatize the two languages. This approach supports step 2 in a 3 step evolution.

1. Treat UML as another implementation language binding like SDAI/C++, not as a data modeling language like EXPRESS. This is what ISO 10303-25 does.
2. Treat UML as a replacement for EXPRESS-G using it for only for schema diagrams. This is what the exff project does.
3. Treat UML and EXPRESS as interoperable/harmonized languages that, in some sense, are simply different representations of the same underlying concept. This requires UML 2 and perhaps changes to EXPRESS in the future.