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Fixed-presentation formats

From: Jason White <jasonw@ariel.ucs.unimelb.edu.au>
Date: Tue, 31 Oct 2000 09:21:45 +1100 (EST)
To: Web Content Accessibility Guidelines <w3c-wai-gl@w3.org>
Message-ID: <Pine.SOL.4.10.10010310855030.13242-100000@ariel.ucs.unimelb.edu.au>
Charles is correct in identifying that problems arise whenever the
presentation is determined by the file format in such a way that the
content can not be manipulated and presented differently as the need
arises. In a typical image file, all structure and semantics are lost.
This is not the case in an SVG image, or in a SMIL presentation, for
example; and as Charles pointed out, in the latter one can at least
separate out the auditory and visual components.

Likewise, PDF 1.3 is superior to PDF 1.2 in that it provides more than the
visual presentation, by allowing the entire structure of the document to
be preserved in the PDF file, with cross-references, in effect, between
the page descriptions and the logical structure.

Thus, there is scope for a checkpoint, subject to user agent support,
which asserts that one should choose the most structurally and
semantically rich format applicable to a given content type.

Here is a (very rough) first attempt:

<dt>Give preference to data formats and software protocols which support
the application of these guidelines.
<dd>
<p>Markup languages, multimedia formats, software interface standards,
etc., vary in the extent to which they support the requirements of
accessibility. In choosing which technologies to use, it is therefore
important to take into account the extent to which they facilitate
application of these guidelines. Content developers should thus favour,
where practicable, solutions which
<ol>
<li>permit text equivalents to be associated with auditory and graphical
content, and multimedia presentations, if applicable, to be synchronized
with text equivalents (guideline 1);
<li>allow the logical structure of the content to be defined,
independently of presentation (guideline 2);
<li>enable the content creator to specify a consistent presentational
style (guidelines 3 and 4);
<li>support device-independent input events (guideline 5);
<li>are documented in published specifications and can be implemented by
user agent and assistive technology developers;
<li>are supported by user agents and assistive technologies
</ol>
<p>Note: to satisfy these requirements, a combination of different
technologies will ordinarily be required.
</dd>

This isn't exactly polished,, draft-quality material and I am offering it
not for inclusion in the next draft, but as a possible line of thinking
that might be discussed and developed further if members of the working
group consider this appropriate.

Opinions herein are my own, personal views.
Received on Monday, 30 October 2000 17:21:53 GMT

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