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STANDARDS for CGM

Standards - ISO 8632; ANSI; FIPS
Amendments - CGM Amendment 1; CGM Amendment 2
Profiles - Model profile; ATA; CALS; PIP; ISP

It all starts with ISO 8632:1992, a.k.a CGM:1992. In a nutshell:

The International Standard - ISO 8632:1992 consists of 4 parts and 2 amendments.

Note: The designation ISO 8632:1992 is equivalent to ISO 8632.1-4:1992. The '.1-4' is used to indicate the part number.

The ANSI Standard - ANSI/ISO 8632.1-4:1992[1994] adopts CGM:1992. (There is no difference)

The FIPS (Federal Information Processing Standard) - adopts ANSI/ISO 8632:1992 and several application profiles.

Application profiles (AP) are subsets of CGM:1992, defined by application communities to promote interoperability among users of the AP. There are several CGM APs:

ISO 8632:1992

ISO 8632:1992 is a graphics data interchange standard which defines a neutral computer interpretable representation of 2D graphical (pictorial) information in a manner that is independent from any particular application or system. The purpose of the standard is to facilitate the storage and retrieval of graphical information between applications, software systems, and/or devices. A CGM can contain:

The CGM standard defines 3 upward compatible versions. Version 1 provides a basic drawing and picture interchange capability. The Version 1 metafile definition includes about 90 elements (i.e., individual function or entity). Version 1 metafiles are essentially the same as the 'old standard', CGM:1987 (see History). The Version 2 metafile definition contain approximately 30 additional elements. (All Version 1 metafile elements are allowed in Version 2 metafiles). The most significant new capability of Version 2, is the graphical segment. A segment is a group of primitives that is saved once and named, and then may be used repeatedly in the metafile. Version 3 metafiles represent a major increase in graphical expressive power. Version 3 metafiles contain about 40 new elements above the Version 2 capabilities. Version 3 metafile functionality includes: the capability to represent compressed tiled images, define external symbol libraries, and greater control of drawing aspects for graphics arts, presentation graphics, and electronic publishing.

Amendments to CGM:1992.

Amendment 1, Rules for Profiles specifies how profiles should be written. Although it adds no new functionality, it provides:

The PPF (profile proforma) is a set of tables which is a template for writing profiles. CGM Amendment 1 requires that all profiles shall include a completed PPF.

ATTENTION PROFILE WRITERS --- It is recommended that the PPF tables be used in conjuction with the Model Profile to write profiles. Use the Model Profile as a starting point from which an application specific profile should be defined. Consider each of the specifications of the Model Profile and either accept the specifications where they are adequate, or modify them when not.

Amendment 2, Application Structuring Extensions addresses the functional requirement for access to arbitrarily small pieces of the metafile or picture. Application areas targeted for this 'intelligent graphics' capability include: electronic review of documents, graphical object databases, network distributed graphical applications, and multi-media and hyper-media documents.
History - The CGM standard was originally published in 1986 by ANSI as X3.122-1986. The same standard was published a year later by ISO as ISO 8632:1987. To make it easier to manage changes, ANSI X3.122:1986 was replaced by ANSI/ISO 8632:1987 in 1991. There were 3 amendments to CGM:1987, two of which are incorporated in the new, republished CGM:1992. The other amendment and CGM:1987 were canceled.

ANSI CGM

The ANSI CGM standard is identical to ISO 8632. The '[1994]' in ANSI/ISO 8632:1992[1994] refers to the year that ANSI officially adopted CGM:1992. The previous ANSI CGM standard, X3.122:1986 is obsolete - throw it out! do not use it!

FIPS 128-2

The FIPS 128-2 (FIPS CGM) adopts ANSI/ISO 8632:1992 and requires the use application profiles. In particular, FIPS CGM requires the use of either the Model Profile, ATA Specification 2100, GREXCHANGE, or CALS MIL-D-28003A. The objective of FIPS CGM includes:

FIPS CGM is applicable for all applications acquired for government use which purport to create or read graphical pictures.

A copy of FIPS 128-2 is available via anonymous FTP on the Internet, the file name is "fips128-2.txt", the file is on "speckle.ncsl.nist.gov" in the "cgm" directory.

FIPS are used for acquisition. They can prescribe the requirements, practices, design, size, etc. of a system. A FIPS may require conformance testing of an implementation.

Application Profiles

An application profile (AP) defines the options, elements, and parameters of ISO 8632 necessary to accomplish a particular function and maximize the probability of interchange between systems implementing the profile. Profiles are defined by application constituencies who agree to adhere to the same subset of CGM for the purpose of graphical data interchange using ISO 8632. A profile addresses metafile requirements as well as generator and interpreter implementation requirements.

There are several prominent profiles:

The Model Profile is defined in CGM:1992. It is a general purpose profile which supports all 3 CGM encodings at the CGM Version 3 functionality level. It is appropriate for basic scientific and technical graphics (e.g., computer-aided design, mapping, earth sciences, cartography) and presentation, visualization, and publishing applications.

The ATA Profile, ATA Specification 2100, has been developed for technical documentation of the manufacture and operation of commercial airplanes. The profile supports the binary and clear text encodings at the CGM Version 3 functionality level. It is appropriate for the exchange of technical manuals, publishing applications, and visualization. The profile supports symbol libraries and will soon incorporate the application structuring of CGM Amendment 2. The profile has been developed and maintained by the ATA/AIA (Airline Transport Assoc. and Airline Industry Assoc.). Information about this profile can be obtained from ATA at 1301 Pennsylvania Ave. N.W., Suite 1100, Washington, D.C. 10004-1707, (202)626-4000

The CALS profile, MIL-D-28003A, was developed by the U.S. Department of Defense for technical illustrations and publications. The profile supports the binary encoding at the CGM Version 3 functionality level. There are many implementations that support this profile at the CGM Version 1 level. This profile does not follow the rules of CGM Amendment 1, since it was produced prior to Amendment 1.

The PIP profile has been developed for graphical interchange between petrotechnical applications in the petroleum exploration and production community. For more information about this profile, contact: Petrotechnical Open Software Corporation, Graphics Metafile Format RFC, 10777 Westheimer, Suite 275, Houston, TX 77042, (713)784-9219

The CGM ISPs are being developed by the EWOS (European Workshop for Open Systems, a regional working interest group of implementors). This work is done under the auspices of ISO and with harmonization with other regional workshops (i.e., OIW in the U.S. and AIW in Asia/Australia) and CGM expert groups (e.g., ANSI X3H3.3, ANSI's CGM standards experts). Four profiles are being developed. Each profile represents a different level of functionality of CGM and complexity of problem that can be solved. Information on these draft ISP's can be obtained from Dr. Anne Mumford, email: A.M.Mumford@lut.ac.uk

April 1996,
comments: jacki.schneider@nist.gov