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RE: Group/Template Support

From: Duncanson, Ian (Ex AS01) <IDuncans@honeywell.com.au>
Date: Thu, 3 Dec 1998 10:42:08 +1000
Message-ID: <384E65A93245D111BAFF00A0C944263BC69E6B@HPACAS01004>
To: "'Jon Ferraiolo'" <jferraio@Adobe.COM>
Cc: www-svg@w3.org
Jon,

I agree it adds a degree of complexity to both the syntax and the
implementation, and off the top of my head I can't think of a really good
reason to have this functionality within the SVG grammar (although I will
keep looking for one). 

The reason for my question (and you'll have to excuse my ramblings, I'm only
just starting to get my head around the possibilities for SVG) is that
graphics templates are used (by my company at least) for two different
purposes -

1)	To provide a "linked shape" that can be pasted into different pages,
and if the original is changed, every page that uses that shape gets
updated. I am guessing that this sort of concept will be available in SVG
via the "standalone packaging" mechanism.
2)	To provide a graphics building block that the author can modify
(stretch, change colors, fonts etc) to suit their need. In this case I guess
the authoring tool itself would need to copy the SVG group object from the
template, thus breaking the link to the template.

I guess the only thing I am not sure whether SVG in the draft format would
provide is access to the child objects of a group object instantiated from a
template via the DOM. If not, this would be a definite need for a lot of
users I would imagine.

The other issue I would like to raise is that the concept of a template and
a group is a great one, but in some ways it seems like an issue that should
be adopted in a higher level XML grammar. As an example of why this might be
necessary, the "shapes" my company currently provides include not only SVG
compatible content such as graphics, images and text, but also binary
components (ActiveX controls etc) referenced through <OBJECT> tags. It would
be great if a template was a true reusable fragment of XML tags that could
be instantiated multiple times (I'm not sure if this can already be done in
XML, but if it can, why do we need the concept of templates in SVG?).

Hope I haven't confused you too much - I know at this stage I am very
confused, but hopefully this e-mail archive will start to clear thing up
once more people get involved.

Regards,
Ian

	-----Original Message-----
	From:	Jon Ferraiolo [SMTP:jferraio@Adobe.COM]
	Sent:	Wednesday, December 02, 1998 2:30 PM
	To:	Duncanson, Ian (Ex AS01)
	Cc:	www-svg@w3.org
	Subject:	Re: Group/Template Support

	Ian,
	I'm a member of the SVG working group, the editor for the SVG
Requirements
	document, and one of the editors for the SVG specification which is
now
	under development.

	These are all open issues right now. Any chance you can express what
you
	would like to see in SVG in these areas, plus how widespread you
think
	these needs might be? We are definitely interested in perspectives
from
	outside of the SVG working group.

	PGML allows object templates (a <graphic>) to contain <group>
objects. (I'm
	not sure about VML.) In our implementations of PGML, we allowed for
	overriding default attributes, but we didn't give a way to override
	attributes on child objects within the object template. Allowing for
	overriding attributes on child objects seems achievable, but it
would mean
	we would have to define a mini grammar for this feature. Do you
think the
	feature justifies the added complexity in the language and the extra
	programming for SVG to support it?

	Thanks.
	Jon Ferraiolo
	Adobe Systems Incorporated

	At 01:26 PM 12/2/98 +1000, you wrote:
	>I am approaching SVG from an editing/authoring tool perspective. 
	>
	>The draft specification mentions support for both collections of
objects (a
	>group) and object templates. With the proposed architecture, will a
template
	>be able to based on a group? If so, how will the SVG syntax cater
for
	>overriding the default attributes of the members of the group?
	> 
Received on Wednesday, 2 December 1998 18:40:36 GMT

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