1. Introduction to WebCGM

This section's subsections are informative, unless otherwise indicated.

1.1 Terminology

This subsection is normative.

The key words words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” are to be interpreted as described in [RFC2119].

1.2 Normative references

This subsection is normative.

ISO/IEC 8632:1999(E): Information technology - Computer graphics - Metafile for the storage and transfer of picture description information
- Part 1: Functional description
- Part 3: Binary encoding
- Part 4: Clear text encoding
Available at the ISO page of Publicly Available Standards. CGM:1999 was reaffirmed by ISO, without changes, at its 5-year review in 2004. The WebCGM profile is defined by reference to the ISO standard.

ISO Register: ISO International Register of Graphical Items, the normative repository of registered extensions to ISO CGM. Available at http://jitc.fhu.disa.mil/nitf/graph_reg/graph_reg.html. An informative summary of registered CGM items, including pointers into the normative register, is available at http://www.cgmopen.org/technical/registry/ .

RFC 3986: Uniform Resource Identifiers (URI): Generic Syntax, Eds. T.Berners-Lee, R.Fielding, L.Masinter, January 2005, available at http://www.ietf.org/rfc/rfc3986.txt .
RFC 3987: Internationalized Resource Identifiers (IRIs), M.Duerst, M. Suignard, January 2005, available at http://www.ietf.org/rfc/rfc3987.txt .
RFC 1951: Deutsch, P., "DEFLATE Compressed Data Format Specification version 1.3", RFC1951, Aladdin Enterprises, May 1996,
URL: http://www.w3.org/Graphics/PNG/RFC-1951
ISO/IEC 10646: ISO (International Organization for Standardization). ISO/IEC 10646-1:2000. Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 1: Architecture and Basic Multilingual Plane and ISO/IEC 10646-2:2001. Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 2: Supplementary Planes, as, from time to time, amended, replaced by a new edition or expanded by the addition of new parts. [Geneva]: International Organization for Standardization. (See http://www.iso.ch for the latest version.)
ISO/IEC 10646-UTF8: ISO/IEC 10646-1:1993, AM2:1996, Information technology — Universal multiple-octet coded character set (UCS) — Part 1: Architecture and Basic Multilingual Plane AMENDMENT 2: UCS Transformation Format 8 (UTF-8). Available from ISO, see http://www.iso.ch.
REC-png: Portable Network Graphics (PNG) Specification (Second Edition) - Information technology - Computer Graphics and image processing - Portable Network Graphics (PNG): Functional specification. ISO/IEC 15948:2003(E). W3C Recommendation 10 November 2003, available at http://www.w3.org/TR/2003/REC-PNG-20031110 .
RFC 2119: IETF RFC 2119: Key words for use in RFCs to Indicate Requirement Levels, S. Bradner, March 1997. Available at http://www.ietf.org/rfc/rfc2119.txt .
XML 1.0: XML 1.0, third edition, Eds. T.Bray, J.Paoli, C.M.Sperberg-McQueen, E.Maler, F.Yergeau, February 2004, available at http://www.w3.org/TR/2004/REC-xml-20040204/ .
Namespaces in XML: Namespaces in XML, Eds. T.Bray, D.Hollander, A.Layman, January 1999, available at http://www.w3.org/TR/REC-xml-names .
RFC 2781: IETF (Internet Engineering Task Force). RFC 2781: UTF-16, an encoding of ISO 10646, Eds. P. Hoffman, F. Yergeau., February 2000. (Available at http://www.ietf.org/rfc/rfc2781.txt )
RFC 3629: UTF-8, a transformation format of ISO 10646, IETF RFC 3629, STD 63, Ed. F. Yergeau, November 2003. (See http://www.ietf.org/rfc/rfc3629.txt )
Unicode: The Unicode Consortium, The Unicode Standard, Version 4, ISBN 0-321-18578-1, as updated from time to time by the publication of new versions. (See http://www.unicode.org/unicode/standard/versions for the latest version and additional information on versions of the standard and of the Unicode Character Database).

1.3 Non-normative references

SVG 1.1: Scalable Vector Graphics (SVG) 1.1 Specification, Eds. J.Ferraiolo, J.Fujisawa, D.Jackson, January 2003, available at http://www.w3.org/TR/SVG11/ .
DOM Level 3 Core: Document Object Model (DOM) Level 3 Core Specification, Eds. A.Le Hors, P.Le Hégaret (plus L.Wood, G.Nicol, J.Robie, M.Champion, S.Byrne), April 2004, available at http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/ .
DOM Level 3 Events: Document Object Model Level 3 Events Specification, Eds. B.Höhrmann, P.Le Hégaret, T.Pixley, April 2006, available at http://www.w3.org/TR/2003/NOTE-DOM-Level-3-Events-20031107..
HTML 4.01: HTML 4.01 Specification, Eds. D.Raggett, A.Le Hors, I.Jacobs, December 1999, available at http://www.w3.org/TR/html401/.
CSS 2.0: Cascading Style Sheets, level 2, CSS2 Specification, Eds, B.Bos, H.Wium Lie, C.Lilley, I.Jacobs, May 1998, available at http://www.w3.org/TR/CSS2/ .
Xpointer Framework: XPointer Framework, Eds. P.Grosso, E.Maler, J.Marsh, N.Walsh, March 2003, available at http://www.w3.org/TR/2003/REC-xptr-framework-20030325/
Cascading Profiles: Definition and description of how to write a profile based on WebCGM as the starting point, for closely related technical application sectors. At http://www.cgmopen.org/technical/cascading-profiles.html
WebCGM 2.0 Requirements: The requirements used to define the new functionality for WebCGM 2.0. At http://www.cgmopen.org/technical/WebCGM_20_Requirements.html
SpecGL 1.0: The W3C QA Framework: Specification Guidelines has guided the inclusion of the normative Conformance clause, and other conformance-related details of WebCGM. Eds. K.Dubost, L.Rosenthal, D.Hazaël-Massieux, L.Henderson,August 2005, available at http://www.w3.org/TR/qaframe-spec/ .
UAAG 1.0: User Agent Accessibility Guidelines 1.0, Eds. Ian Jacobs, Jon Gunderson, Eric Hansen, 17 December 2002, a W3C Recommendation available at
http://www.w3.org/TR/2002/REC-UAAG10-20021217/
WCAG 1.0: Web Content Accessibility Guidelines 1.0, Eds. Wendy Chisholm, Gregg Vanderheiden, Ian Jacobs, 5 May 1999, a W3C Recommendation available at http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505/ .

1.4 About WebCGM

The scope of this WebCGM^TM 2.0 specification includes three components:

an intelligent graphics profile of the ISO Computer Graphics Metafile (CGM) standard (ISO/IEC 8632:1999), tailored to the requirements for scalable 2D vector graphics in electronic documents on the World Wide Web;
a WebCGM Document Object Model (DOM), which provides an application programming interface to WebCGM objects in WebCGM-supporting applications;
definition of a standard WebCGM XML Companion File (XCF), which allows applications to externalize some non-graphical metadata from WebCGM instances, yet maintain a tight binding of the metadata to WebCGM objects.

WebCGM is a set of specifications targeted especially at the effective application of the ISO CGM:1999 standard to representation of 2D graphical content within Web documents.

CGM has been an ISO standard since 1987, and CGM has been a registered media type (image/cgm) for the Internet and the World Wide Web since December 1995. WebCGM 1.0, comprising the original intelligent graphics profile of ISO CGM, was first published in 1999, was re-released in 2001 with error corrections, and forms the basis for the WebCGM 2.0 intelligent graphics profile of this WebCGM 2.0 specification.

For much more information about WebCGM, please see the WebCGM FAQ, as well as other numerous other references and reading materials, on the OASIS CGM Open Web site.

1.5 The WebCGM profile and profile rules

The WebCGM profile is a conforming profile of ISO CGM under the stipulations of CGM:1999 Clause 9, "Profiles and conformance", and it utilizes the Profile Proforma (PPF) of CGM:1999 Annex I.1, Proforma tables, for representation of the element-by-element content details.

The WebCGM profile is an "intelligent graphics" profile, which means that in addition to graphical content based on CGM Versions 1-3, the profile includes non-graphical content based on CGM Version 4, Application Structures. The non-graphical content allows the definition of hierarchies of application objects, as well as the association of metadata, such as link specifications and layer definitions, with the objects.

1.6 WebCGM requirements

The original WebCGM 1.0 profile resulted from a collaboration between the CGM Open Consortium and W3C Graphics Activity. The requirements that determined the content selection for CGM 1.0 were derived from:

the requirements articulated in the document "W3C Scalable Graphics Requirements" (http://www.w3.org/Graphics/ScalableReq [grfreq]);
the specifications and requirements defined in "Use of CGM as a Scalable Graphics Format" (http://www.w3.org/TR/NOTE-cgm [cgmreq]);
technical recommendations from the CGM Open Consortium (see http://www.cgmopen.org/).

The selection criteria for the WebCGM profile include:

graphical content: it should have high expressive power; and, it should be both widely implemented, and implementable with a reasonable level of effort.
intelligence content (structuring and metadata elements): criteria came from the above-mentioned requirements document, [cgmreq], plus additional requirements generated during the first 5 years of deployment and use of the WebCGM 1.0 standard.

The upgraded content of the WebCGM 2.0 profile -- a set of additions, deletions, and modifications applied to the 1.0 profile -- has been shaped by:

additional requirements generated during 5 years of deployment of WebCGM 1.0 in industry;
apparent non-use of certain 1.0 features;
need for convergence with similar profiles in closely related industries.

The DOM and XCF components of WebCGM 2.0 derive from requirements generated during 5 years of deployment of WebCGM 1.0 in industry. The WebCGM 2.0 Requirements document summarizes these requirements.

1.7 WebCGM and other profiles

The WebCGM 2.0 intelligent graphics profile, like its predecessor WebCGM 1.0, is a profile of the ISO CGM:1999 standard, designed for effective application of CGM in technical Web applications. WebCGM is not aimed at or optimized for any particular technical application sector, but is intended to satisfy general requirements shared by different but closely related technical Web applications.

Following five years of deployment and application of WebCGM and other technical profiles (such as Air Transport Association's), some divergence began to appear. WebCGM 2.0 represents a major effort towards convergence of intelligent graphics profiles in closely related industries. In fact, it is the intention of the authors and publishers of WebCGM 2.0 that it be used as a basis for the definition of industry-specific profiles. The use of WebCGM as a core profile from which specific-industry technical profiles are derived and defined is defined in Cascading Profiles.

1.8 Editions and releases of WebCGM

CGM:1999 Clause 9, "Profiles and conformance", prescribes that profiles shall maintain revision control by using a standard "ProfileEd" keyword. Instances of a profile carry this edition information in their identification section. Prior releases of WebCGM include:

WebCGM Profile, 21 January 1999, the first release of WebCGM ("ProfileEd:1.0").
WebCGM 1.0 Second Release, 17 December 2001, an errata-correcting release of the previous (also "ProfileEd:1.0").

This specification is the first release of WebCGM 2.0 ("ProfileEd:2.0"). There may be future releases of WebCGM 2.0, for maintenance and defect correction. There may be future higher editions and versions of WebCGM (e.g., 2.1).

1.9 Roadmap to this specification

WebCGM is written in these major sections:

This section, containing introductory and overview material, which is mostly informative, but does contain two normative subsections.
A WebCGM Concepts section, informative but not normative.
Detailed descriptive material on the V4 content of WebCGM, including Content Model which can be used for V4 content. This section is normative.
The definition of a standard XML Companion File (XCF) for use with WebCGM. This section is normative.
The definition of the WebCGM Document Object Model (DOM). This section is normative (including normative IDL definitions of the DOM interfaces).
The Profile Proforma (PPF), comprising an extensive table which addresses every element of the ISO CGM standard, per CGM:1999 Annex I. This section is normative.
The normative Conformance chapter describes the conformance targets and conformance details of WebCGM.
The ECMAScript chapter give a normative description of an ECMAScript binding for WebCGM DOM.
Appendixes, including informative sections such as revision history, comparison of WebCGM 1.0 and 2.0, etc.

1.10 Document sources and registration authority

This subsection is informative (non-normative).

Copies of the ISO standards may be obtained from ISO:

ISO Central Secretariat
1, rue de Varembe
Case postale 56
CH-1211 Geneve 20
Switzerland

For the purpose of this Recommendation and according to the rules for the designation and operation of registration authorities in the ISO/IEC Directives, the ISO and IEC Councils have designated the following as the registration authority:

National Imagery and Mapping Agency (NIMA)
(Joint Interoperability Test Command)
The Registration Authority for Graphical Items
Building 57305
Fort Huachuca
Arizona
85613-7020
USA

For more information on the CGM standard itself, the CGM Open Web site has both bibliographic references, and short articles on CGM topics:

CGM Open: http://www.cgmopen.org/

The following World Wide Web sites have more information on CGM:

ISO/JTC1/SC24: http://www.cwi.nl/JTC1SC24/
W3C WebCGM Overview: http://www.w3.org/Graphics/WebCGM

WebCGM 2.0 — Introduction to WebCGM

Contents