CGM is the abbreviation for Computer Graphics Metafile. Within the CALS Initiative (Computer-Aided Acquisition and Logistic Support), CGM has been defined as a standard format for device-independent 2D files. The purpose of the CGM file is to store all illustrations so that they can be read and interpreted unambiguously by compliant programs.

CGM is used as a standard format in many different industries including the aerospace (ATA, AECMA), automotive (J2008), defense (CALS), telecommunications, and petrochemical industries among others. An area of growing importance for the use of CGM files is the Web environment (Internet and intranets). Here, intelligent graphics in the WebCGM format are used to generate interactive catalogs and manuals.

CGM is defined as a standard in ISO 8632. The first issue appeared in 1987 and described CGM version 1, which suffered significant criticism. One particularly unfortunate aspect was its very small stock of graphic primitives, with no Bézier or spline curves defined at all. Consequently, all curves have to be written as polylines, which leads to major disadvantages during further processing.

The communication difficulties become even more apparent given that the Bézier curve constitutes a key element of almost all PostScript-oriented programs running on various platforms (PostScript only knows Bézier paths). Moreover, there is no direct link to PostScript.

Following the addition of a number of segments and other details in 1990 (version 2), an extended version of the ISO standard was published in 1992 and now incorporates version 3 of CGM. This version is much better suited for storing high-quality illustrations.

CGM version 3 was extended to include “application structures” in 1995 and therefore gave rise to CGM version 4. This means that non-graphic information can now also be saved in a CGM file. This combination opens up a whole series of possibilities as regards interactive graphics, hot spots, hyperlinking, etc.

The current version of the CGM standard was published at the beginning of 2000 and corrects several problems found in former releases. No new functionality has been added.

The CGM Open Consortium was founded in 1998 with the aim of promoting and developing CGM. Software manufacturers and customers who use CGM have joined forces in this organization to tackle the challenges involved in working with CGM. Together with the World Wide Web Consortium (W3C), CGM Open has developed the “WebCGM” profile, which standardizes the use of CGM files in Internet environments.

Arbortext IsoDraw provides the most extensive support currently available for reading and writing CGM files. You can even set CGM as the standard format so that only CGM is used instead of the Arbortext IsoDraw format. This setting is described in the following paragraphs.