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Re: [SVGMobile12] Interaction with XLink

From: Ian Hickson <ian@hixie.ch>
Date: Sun, 29 Jan 2006 04:39:28 +0000 (UTC)
To: Charles McCathieNevile <chaals@opera.com>
Cc: www-svg@w3.org
Message-ID: <Pine.LNX.4.62.0601290431210.9516@dhalsim.dreamhost.com>

On Fri, 27 Jan 2006, Charles McCathieNevile wrote:
> > 
> > it is unclear what XLink-aware user agents should do when facedwith 
> > SVG Tiny 1.2 content that explicitly sets the XLink 
> > attributes,especially now that no DTD is used and therefore the XLink 
> > attributesdon't normally have their correct values.
> 
> Where the attributes are explicitly set (by which I mean are present in 
> the source of the SVG content in question), they should be interpreted 
> as per the Xlink specification (see also your other question, below).

This seems to contradict the SVG specification, which implies that, e.g., 
the following:

   <svg xmlns="http://www.w3.org/2000/svg" 
        xmlns:xlink="http://www.w3.org/1999/xlink">
     <a xlink:href="test" xlink:show="embed" xlink:type="simple">
       <rect width="100%" height="100%"/>
     </a>
   </svg>

...should render a black rectangle that is a link, whereas per XLink that 
link should render the file "test" in place of the black rectangle.

Please clarify the SVG specification to state exactly how XLink attributes 
with unexpected values are to be handled in an SVG context.

Please include a test to this effect in the SVG test suite.


> If you meant to ask about when they are set *implicitly* (i.e. 
> attributes for which default values are defined in the SVG specification 
> are not present in the source of the content), for an SVG user agent 
> which implements Xlink, it should supply the default values as specified 
> by SVG, and for a user agent which implements Xlink but not SVG it 
> should follow the behaviour specified by the Xlink specification.

I do not understand why SVG is changing XLink semantics. The XLink 
specification doesn't seem to allow for attributes to be implied by 
mechanisms other than DTDs.

In particular, per XLink, this should not create a link:

   <svg xmlns="http://www.w3.org/2000/svg" 
        xmlns:xlink="http://www.w3.org/1999/xlink">
     <a xlink:href="test">
       <rect width="100%" height="100%"/>
     </a>
   </svg>

Please clarify the SVG specification to state exactly how XLink semantics 
are being changed.


> > Please clearly define, for all SVG elements, how XLink attributes must 
> > be treated when they do not have their expected values.
> 
> In this case the document is a non-conforming SVG document, and so 
> should be treated as such. In practice, this means the attribute in the 
> content is ignored.

This seems to directly contradict the XLink specification.

Please change the SVG specification such that a UA can implement XLink and 
SVG simultaneously without violating either specification.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Sunday, 29 January 2006 04:39:39 GMT

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