Overview

The Standard for the Exchange of Product Model Data (STEP) is a comprehensive ISO standard (ISO 10303) that describes how to represent and exchange digital product information. STEP was born in 1983, and was based on previous national efforts such as IGES, VDAFS, SET, CAD*I, and PDDI.

The first parts of the STEP standard were issued as international standards in 1994, including the first application protocol, AP203, and over the following two years, geometry exchange became reliable. More protocols are under development to address other types of engineering information, such as machine-tool controls (STEP-NC) and product data management (PDM).

The Structure of STEP

Digital product data must contain enough information to cover a product's entire life cycle, from design to analysis, manufacture, quality control testing, inspection and product support functions. In order to do this, STEP must cover geometry, topology, tolerances, relationships, attributes, assemblies, configuration and more.

To accomplish this ambitious goal, STEP has been constructed as a multi-part ISO standard. The basic parts are complete and published, while more are under development. These parts cover general areas, such as testing procedures, file formats and programming interfaces, as well as industry-specific information. The most important aspect of STEP is extensibility. STEP is built on an language that can formally describe the structure and correctness conditions of any engineering information that needs to be exchanged.

Industry experts use this language, called EXPRESS, to detail the information required to describe products of that industry. These "Application Protocols" form the bulk of the standard, and are the basis for STEP product data exchange. In addition, the EXPRESS language can document constraints as well as data structures. These formal constraints are an explicit correctness standard for the digital product data.

The figure below shows the structure of the STEP standard. Infrastructure parts, such as the exchange file format (Part 21), have been separated from industry-specific parts, such as the application protocol for configuration-controlled designs (Part 203, also called AP203). Most of the infrastructure is complete, but industry-specific protocols are open-ended. Application protocols are available for mechanical and electrical applications, and are under construction for composite materials, sheet metal dies, automotive design and manufacturing, shipbuilding, the AEC industry, process plants, and others. Over time, many industries will develop their own APs.

Structure of the STEP Standard.

Some Reasons Why STEP is Important