The Initial Graphics Exchange Specification (IGES) (pronounced eye-jess) defines a neutral data format that allows the digital exchange of information among Computer-aided design (CAD) systems.
The official title of IGES is Digital Representation for Communication of Product Definition Data, first published in January, 1980 by the National Bureau of Standards as NBSIR 80-1978. Many documents (like the Defense Standards MIL-PRF-28000B and MIL-STD-1840C) refer to it as ASME Y14.26M, the designation of the ANSI committee that approved IGES Version 1.0.
Using IGES, a CAD user can exchange product data models in the form of circuit diagrams, wireframe, freeform surface or solid modeling representations. Applications supported by IGES include traditional engineering drawings, models for analysis, and other manufacturing functions.
The IGES project was started in 1979 by a group of CAD users and vendors, with the support of the National Bureau of Standards (now known as NIST) and the U.S. Department of Defense (DoD). The name was carefully chosen to avoid any suggestion of a database standard that would compete with the proprietary databases then used by the different CAD vendors.
Since 1988, the DoD has required that all digital Product Manufacturing Information (PMI) for weapons systems contracts (the engineering drawings, circuit diagrams, etc.) be delivered in electronic form, specifically in IGES format. As a consequence, any CAx software vendor who wants to market their product to DoD subcontractors and their partners must support the import (reading) and export (writing) of IGES format files.
An ANSI standard since 1980, IGES has generated warehouses full of magnetic tapes and CD-ROMs of digital PMI for the automotive, aerospace, and shipbuilding industries, as well as for weapons systems from Trident missile guidance systems to entire aircraft carriers. These part models may have to be used years after the vendor of the original design system has gone out of business. IGES files provide a way to access this data decades from now. Today, plugin viewers for Web browsers allow IGES files created 20 years ago to be viewed from anywhere in the world.
After the initial release of STEP (ISO 10303) in 1994, interest in further development of IGES declined, and Version 5.3 (1996) was the last published standard. A decade later, STEP has yet to fulfill its promise of replacing IGES, which remains the most widely used standard for CAx and PMI interoperability.
A Recursive Standard
One of the unique features of the IGES standard is that it was the first ANSI Standard to be documented using itself. Since Version 4.0, all of the technical illustrations for the printed version of the standard have been generated from IGES files. The electronic publishing system (LaTeX) integrates raster images generated from IGES files into the PostScript sent to the laser jet computer printer, so text and images are printed on the same page for subsequent use as camera-ready copy for commercial publication. Beginning with IGES Version 5.2, this is how the standard was generated, and Version 5.3 (the most recent ANSI approved version) is available as a PDF document.
Many of the illustrations (all of which conform to the Defense Department's MIL-D-28000 Engineering Drawings Subset of IGES) use the entities that they describe, e.g., the illustration of the LEADER (ARROW) ENTITY (Type 214) can be used as a test case for translator implementers, because it contains all 12 arrow head styles defined by the standard.