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ANN: SVG browser with expression based attribute values

From: Cameron McCormack <clm@csse.monash.edu.au>
Date: Fri, 18 Jul 2003 18:15:43 +1000
To: www-svg@w3.org, svg-developers@yahoogroups.com
Cc: Kim.Marriott@infotech.monash.edu.au, bernd.meyer@acm.org
Message-ID: <20030718081543.GA4304@jade.bpa.nu>

The recent SVG 1.2 Working Draft has suggested that SVG is extended
in some way to allow expressions as attribute values and for these
expressions to be evaluated at display-time to determine the attribute
value (3.2.7 Expression-based attribute values).  Potentially this
extension is very useful for supporting widget layout and dynamic
layout, two of the aims of SVG 1.2.

In order to better explore the capabilities that expression-based
attributes allows we have extended Batik to provide this ability and
have built several representative examples illustrating the extra
power.  The examples demonstrate that adding dynamic evaluation of
expression-based attribute values to SVG allows the SVG author to:

  - specify how to adjust the SVG layout in response to viewer
    requirements and the viewing environment such as a small browser
    window on a PDA,

  - specify widget layout which adjusts to the viewing context.  In
    particular it is relatively easy to specify grid-based widget layout
    and widget placement and size which is fixed regardless of zooming
    on other parts of the SVG document,

  - and expression-based attribute values provide support for user
    interaction since the expressions can be in terms of variables
    set by the user during interaction.

An advantage of adding dynamic evaluation of expression-based attributes
to SVG itself is that one-way constraint solving is considerably less
expensive to support than scripting and probably RCC.  This means that
less powerful mobile computing devices could support dynamic evaluation
of expression-based attributes and get many of the benefits of RCC
(widget layout, dynamic layout) without needing to support full RCC and

For information on the project, please visit:


where you can read about the extensions, see some examples and download
the program.


Cameron McCormack
  // clm@csse.monash.edu.au
  // http://www.csse.monash.edu.au/~clm/
  // icq 26955922
Received on Friday, 18 July 2003 04:15:53 UTC

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