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Re: SVG vs. WebCGM

From: Chris Lilley <chris@w3.org>
Date: Tue, 12 Sep 2006 16:04:53 +0200
Message-ID: <403273570.20060912160453@w3.org>
To: "Jeff Schiller" <codedread@gmail.com>
Cc: public-webcgm@w3.org

Hi Jeff,

On Tuesday, September 12, 2006, 4:08:25 AM, you wrote:

JS> You knew someone would ask this eventually, I'm surprised the
JS> charter doesn't mention it.

(Agreed the WebCGM WG charter does not mention it).

It has come up many years ago, in fact. The comparison was discussed at
several XML conferences, for example XML Europe 2001:

SVG and WebCGM – A Comparison
Chris Lilley, Graphics Activity Lead, W3C, France;
Dieter Weidenbrück, CEO, ITEDO Software, Germany


a later, more up to date comparison

JS> What is the differences in SVG and WebCGM?  Is SVG intended as
JS> general/all-purpose while WebCGM is only for technical/industrial
JS> drawings?  This seems like a rather arbitrary distinction.

The main difference is field of use. The industrial technical graphics
community picked CGM many years ago, its is today very widely used in a
particular market segment (primarily defence, aerospace, and

Those users wanted an evolutionary improvement to add reliable,
vendor-neutral web linking; this requirement was met by WebCGM 1.0.

At the same time, CGM has some limitations. Its not easily stylable with
either CSS or XSLT; it is not in XML; it lacks the graphical richness
needed for design intensive graphics; it has no animation capability.

This is why SVG was started, after W3C had grappled with CGM (over the
period 1996 to 1998). http://www.w3.org/TR/1998/WD-SVGReq-19981029

In general, WebCGM can be converted to SVG 1.1 without loss[1]. Even in
the technical graphics community, SVG is also used for training
materials etc (which need animation and more graphical richness) but the
long lifecycle technical documentation still needs to use CGM. WebCGM 1
and WebCGM 2 are still valid ISO CGM and thus can be used in systems
whose requirements were drawn upin the mid 1980s.

Note that tools for generating WebCGM, such as ISODraw, often export to
SVG as well.

Some features from SVG, such as having a DOM, are now being added to
WebCGM 2.0; but the main driver for WebCGM 2.0 is five years of
industrial experience with WebCGM 1.0.

JS> Why do we need two standards for scalable vector web graphics?  Can
JS> someone outline the purposes, distinctions, directions of these two
JS> seemingly competing standards within the W3C ?

Hopefully the above clarifies this to some extent. Happy to answer
follow-on questions.

[1] 99.5%, anyway - the CGM name attribute behaves like a non-unique ID
and XML does not have such a construct.

 Chris Lilley                    mailto:chris@w3.org
 Interaction Domain Leader
 Co-Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Tuesday, 12 September 2006 14:05:19 UTC

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