Since 1984 the International Organization for Standardization (ISO) has been working on the development of a comprehensive standard for the electronic exchange of product data between computer-based product life-cycle systems. Initial concentration has been on design and manufacturing applications. This standard, ISO 10303 [1, 2, 3] , is informally known as STEP (STandard for the Exchange of Product model data). Its scope is much broader than that of other existing CAD data exchange formats, notably the Initial Graphics Exchange Specification (IGES), a US standard that has been in use for nearly twenty years. Whereas IGES was developed primarily for the exchange of pure geometric data between computer aided design (CAD) systems, STEP is intended to handle a much wider range of product-related data covering the entire life-cycle of a product. The development of STEP has been one of the largest efforts ever undertaken by ISO. Several hundred people from many different countries have been involved in the work for the past sixteen years, and development is as active now as it ever has been in the past. STEP is increasingly recognized by industry as an effective means of exchanging product-related data between different CAD systems or between CAD and downstream application systems [4] . The first parts of the standard were published in 1994 [1,2] after some ten years of work by members of the relevant standards subcommittee, ISO TC184/SC4, whose responsibility is Industrial Data'. Much of this effort went to developing an infrastructure for the standard that will ensure its extensibility for the foreseeable future. ISO 10303 covers a wide variety of different product types (electronic, electro-mechanical, mechanical, sheet metal, fiber composites, ships, architectural, process plant, furniture,...) and life-cycle stages (design, analysis, planning, manufacture,...). This range is continually expanding as new parts of the standard are issued. These parts are referred to as ISO 10303-xxx, where xxx is the part number, and each is a standard in its own right, despite being a component of a larger whole and interdependent on other parts. Currently the overall standard is composed of about 40 parts, though many more are in development. At present ISO 10303 exchanges usually employ the well-known neutral file approach, in which transfer between two systems is a two-stage process. In Stage 1 data is translated from the native data format of the originating system into the neutral ISO 10303 format, and Stage 2 is translation from the neutral format into the native format of the receiving system. The actual exchange medium in this case is an ASCII file. However, the standard makes a separation between the information model and its physical implementation, and this permits ISO 10303 models also to be used in other ways. For example, ISO 10303-022 has
ISO 10303 (STEP) REF is an ISO standard for product manufacturing information, i.e., how a product is supposed to be produced, but it can be used for the whole life cycle of a product.
Introduction to ISO 10303, the STEP Standard for Product Data Exchange
ASME J. Computing and Information Science in Engineering
Engineering Computer Science