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Last modified: April 23, 2004
Computer Graphics Metafile (CGM)


[Provisional topic document on CGM; under construction 2004-04]

Initiatives and Specifications

CGM Open

"CGM Open is an international organization of vendors and users dedicated to open and interoperable standards for the exchange of graphical information. CGM Open is an affiliate member of OASIS, the XML interoperability consortium. The work of CGM Open complements that of standards bodies, focusing on making Web graphics standards easy to adopt and practical to use in real world, open systems applications.

CGM Open developed and currently maintains WebCGM, an application of the ISO-standard Computer Graphics Metafile for electronic documents. WebCGM was developed in collaboration with the W3C, with support from the European Commission Esprit project. An "intelligent graphics" profile, WebCGM includes both graphical and non-graphical content, allowing object hierarchies, link specifications and layer definitions... [from the CGM Open website]


ISO 8632:1992 - Computer Graphics Metafile (CGM)

The CGM (Computer Graphics Metafile) standard is an "international standard for the open interchange of structured graphical objects and their associated attributes." It is defined in ISO 8632:1992 together with Amendments 1 and 2, and specifies a two-dimensional data interchange standard which allows graphical data to be stored and exchanged among graphics devices, applications, and computer systems in a device-independent manner. It is a revisable, structured format that can represent vector graphics (e.g., polylines, ellipses, NURBS), raster graphics, and text. Although initially a vector graphics format, it has been extended in three upwardly compatible extensions to include raster capabilities and provides a very useful format for combined raster and vector images. A metafile is a collection of elements. These elements may be the geometric components of the picture, such as polyline or polygon. They may be details of the appearance of these components, such as line colour. They may be information to the interpreter about how to interpret a particular metafile or a particular picture. The CGM standard specifies which elements are allowed to occur in which positions in a metafile." [adapted from NIST document]


OASIS CGM Open WebCGM Technical Committee

In April 2004 a new CGM Open WebCGM Technical Committee was formed at OASIS to accelerate the further adoption, application, and implementation of the Computer Graphics Metafile (CGM). CGM is an "international standard for open interchange of structured graphical objects and their associated attributes. The WebCGM Profile of CGM was developed by CGM Open and is a current recommendation of the W3C. WebCGM is focused on presenting dynamic technical graphics in the web environment." New work for the OASIS TC, according to the scope statement, includes possible releases of new versions of WebCGM, WebCGM DOM development, Web-based CGM interoperability reporting and tracking system, alignment of WebCGM functionality with ATA and other graphics profile requirements, definition of semantics of XML companion data associated with WebCGM, and production of an XML encoding of WebCGM. The group may identify additional interoperability topics in response to the evolution of world markets, target application sectors, and CGM/WebCGM implementations. It will develop an education program for users and implementers of CGM and WebCGM technology as needed. The TC Convenor and Proposed Chair are Dave Cruikshank (Boeing). The first meeting of the CGM Open WebCGM TC will be held May 24-27, 2004 as a F2F meeting in Cologne, Germany, hosted by ITEDO.


W3C WebCGM Profile

"CGM (Computer Graphics Metafile) has been an ISO standard for vector and composite vector/raster picture definition since 1987. CGM has a significant following in technical illustration, interactive electronic documentation, geophysical data visualization, amongst other application areas and is widely used in the fields of automotive engineering, aeronatics, and the defence industry.

WebCGM is a profile for the effective application of CGM in Web electronic documents. WebCGM has been a joint effort of the CGM Open Consortium, in collaboration with W3C staff and supported by the European Commission Esprit project. It represents an important interoperability agreement amongst major users and implementors of CGM, and thereby unifies current diverse approaches to CGM utilization in Web document applications. WebCGM's clear and unambiguous conformance requirements will enhance interoperability of implementations, and it should be possible to leverage existing CGM validation tools, test suites, and the product certification testing services for application to WebCGM.

While WebCGM is a binary file format and is not 'stylable', nevertheless WebCGM follows published W3C requirements for a scalable graphics format where such are applicable. The design criteria for the graphical content of WebCGM aimed at a balance between graphical expressive power on the one hand, and simplicity and implementability on the other. A small but powerful set of metadata elements is standardized in WebCGM, to support the functionalities of: hyperlinking and document navigation; picture structuring and layering; and, search and query on WebCGM picture content..." [principal web page]


General Resources

Articles, Papers, News

  • "Validation of a CGM Graphic Against the Web CGM Profile." By Stuart Galt (The Boeing Company). Presented at XML Europe 2002. "The adoption of the XML Schema Specification by the W3C makes it possible to create machine processible application profiles of formats other than XML. WebCGM is an application profile of the CGM standard which enables to deployment of CGM in the web environment. WebCGM is encoded as binary data and the syntax is much richer than can be expressed rigorously with XML DTD syntax. However, binary CGM can be translated into an XML instance but XML validation tools are not sufficient. By creating an XML Schema to describe the WebCGM profile the XML instance of CGM may be validated using the standard schema tools available, reducing the needs to use proprietary methods that work directly with the binary CGM." Also in PDF format [cache]

  • "WebCGM and SVG: A Comparison." By Chris Lilley and Dieter Weidenbr|ck. Paper prepared for XML Europe 2001. 8 pages. [source PDF]

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