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Re: SVG12: linking restrictions vs AWWW

From: Chris Lilley <chris@w3.org>
Date: Tue, 7 Feb 2006 12:36:54 +0100
Message-ID: <688101033.20060207123654@w3.org>
To: Maciej Stachowiak <mjs@apple.com>
Cc: Bjoern Hoehrmann <derhoermi@gmx.net>, www-svg@w3.org

On Sunday, February 5, 2006, 11:20:51 PM, Maciej wrote:

MS> On Feb 5, 2006, at 7:44 AM, Chris Lilley wrote:

>> Perhaps you could list the limited set of URI schemes that you  
>> claim SVG
>> constrains people to, or the language that you believe limits the URI
>> schemes that can be used?

MS> In the chart Bjoern linked, there is a separate column for what  
MS> elements support "data:" URIs when linking. This implies that either  
MS> some elements support other URIs but not data:, or that some elements  
MS> support data: URIs but not others.

The columns need to be considered together. Some elements support
linking between one document and another one; some elements are
constrained to point to the current document.

Elements that can only point to the current document cannot use data:
URIS - as a consequence, not as an isolated restriction - because the
data: scheme always conveys a complete resource which is a separate
document.

Contrast this with other schemes - http, file, rtp, etc - where a URI
could indeed still point to the current document if it happens to have
the same base. The peculiar nature of the data: scheme means that it can
never point to the current document. The table notes this.

SVG does not constrain URIs to be a limited set. For example, it does
not say "you can only use http" which would be an example of such a
restriction.

MS> Just scanning the chart quickly, I found this to be the case for  
MS> "use" and "prefetch" elements. Some elements also have restrictions  
MS> on non-data URIs (such as requiring that they have a fragment  
MS> reference) that are not applied to "data:" URIs, for example "font- 
MS> face-uri" requires a fragment ID on the URI which refers to an SVG  
MS> font element but places no such restriction on "data:" URIs.

data: URIs cannot have fragment identifiers, as noted in previous last
call comments.

MS> It would be better to treat data: URIs just like all others and have  
MS> no separate column for what elements support them.

We could remove that column and let people figure it out for themselves,
but we added this detailed information in response to last call comments
in the previous round.


-- 
 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Tuesday, 7 February 2006 11:36:48 UTC

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