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Including OBJECTs in ML's

From: Jim Ley <jim@jibbering.com>
Date: Mon, 21 Oct 2002 19:05:53 -0000
Message-ID: <01e901c27934$e125b400$ca969dc3@emedia.co.uk>
To: "WAI Cross-group list" <wai-xtech@w3.org>

Hi,

I've been thinking about OBJECT and the various specs/implementations
we have, and I've found a few issues, as they cross various groups and
are somwhat XAGy aswell, I'm raising them here first - I hope that's
ok.

The first issues are to do with negotiation:

If you wish to use content-negotiatation to serve up an appropriate
image format (as the W3 does with its logo) you need to leave the type
of object blank, or have it wrong, the disadvantage of having it
blank, is that the UA has to make a GET request even to identify the
mime-type of the resource somewhat wasteful if you don't want images
downloaded for example.  I think this one has an easy solution, ensure
that content-type can contain a list, and allow wildcards, i.e. in
HTML:

<object type="image/*" ... >

The other issue with choice in included content is that none seem very
powerful, for example in SVG we have the switch element for choosing
alternatives, and this is a strict heirachy, use A before B.  Often
though A and B are of equal quality and it should be up to the user which
they would prefer, other times though B is much worse quality and they
should only use it if they can't cope with A at all.  In http
content-negotiation you can do this via the q value - I think it would be
very useful to have the same in ML's

Consider SVG:

<switch>
  <text systemLanguage="en">Yes</text>
  <text systemLanguage="de">Ja</text>
</switch>

Here the two languages are clearly equivalent, however the English will
always take priority.  However there may be a poor quality translation of
the text in second languages and in that situation it would be useful to
distinguish it from the first.  (I think this applies to all
included/negotiated content, not just language choices)  I'm not sure of
a solution to this one, perhaps simply a q value on each attribute.

In HTML, OBJECT is different from embed/image - if I include an SVG in a
page with EMBED links from that svg document replace the HTML page, if I
do it with OBJECT they replace only the FRAME of the SVG * in fact
there's no way to include content which is actually part of the same
document as we currently in HTML.  To solve this I think we need to have
different types of OBJECT, one a way of including content that is part of
the Document, and another a way of including a Sub-Document - as they
serve different purposes, and are used for different types, consider:

<object type="image/svg+xml" ... >
 <object type="text/html" ... >
  <object type="image/jpeg"  usemap="#map" ...>
   <a ... > somewhere else </a>
  </object>
 </object>
</object>

Here links from the SVG document will open within the SVG "FRAME", the
HTML within the HTML "frame", but the jpegs links from the image map will
open in the parents window, this difference is somewhat difficult to
resolve with different media types.

Cheers,

Jim.

* Actually it appears they don't where OBJECT works with SVG, however I
believe this is wrong as otherwise we have a difference between HTML and
SVG which I don't think can be explained, this maybe controversial
though.
Received on Monday, 21 October 2002 15:07:48 GMT

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