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ACTION-78 - Rewrite 3.2.2 to allow user to choose any combination of alternatives to be rendered

From: Jim Allan <jimallan@tsbvi.edu>
Date: Tue, 18 Nov 2008 14:02:20 -0600
To: <w3c-wai-ua@w3.org>
Message-ID: <00de01c949b8$90aff2f0$b20fd8d0$@edu>

Should be combine 3.2.2 and 3.2.4
3.2.2 Configurable Default Rendering: The user has the global option to set
preferences for which alternative(s) are rendered by default. (Level A)
@@2.9 in UAAG10@@

3.2.4 Simultaneous Rendering: The user has the option to simultaneously
render any and all items from the alternative content stack (which will
cause the document to reflow accordingly) unless the user agent can
recognize a mutual exclusion (e.g., conflicting soundtracks). (Level AA)

Combining the success criteria seems untenable. First they are different
levels - A and AA. After much thought and review of our work, I need to get
to the basics...

Guideline 3.2 Provide access to alternative content. 
For Synchronized media, the user needs 3 things
a. notification of available alternatives, if any
b. ability to select and render from among non-competing alternatives (can't
render 2 audio tracks simultaneously)
c. ability to configure default rendering based on a cascade (availability) 
	(e.g. video - yes; low-bandwidth | high-bandwidth
	caption - yes; English | French | default 
	video-description - no; 
	sign-language - yes; ASL | English | default)

For non-synchronized media, the user needs 3 things
a. notification of available alternatives, if any
b. ability to select and render from among alternatives 
c. ability to configure default rendering based on a cascade (availability)
(e.g. alt | title | longdesc | image)

note: The markup language defines what constitutes alternative content. The
languages are changing, as are alternatives to content. UAWG cannot
prescribe for which alternatives notification, selection, and rendering must
be provided. UAWG can only say that the above listed functionality must be
provided in order to have a conforming and accessible user agent. 

I have a concern about alternative content that is 'nested' in (or
is_a_child_of) the original content. Currently, in the <object> element,
alternative content maybe provided inside the inside the element. If the
'original' content is not rendered (i.e. the plug-in is not available), then
the 'nested' (call it alternative or fall-back content) is revealed.
Scenario, user has flash installed, author provided alternative/nested
content in the <object>, the flash is inaccessible for the users assistive
technology. Currently, the user cannot gain access to the author provided
alternatives without uninstalling flash or wading through the source code of
the page. 
The user must have access to that 'nested' content even if the 'original'
content is rendered. This 'nested' content must be considered 'alternative'
content and made available to the user via the functionality listed above. 

The rewording of 3.2.2 applies to 'c' above. The guideline should be
renumbered to reflect the hierarchy of notification, selection,

3.2.2 Provide a global option to configure default rendering for
non-synchronized media based on a cascade of available alternatives that can
be rendered as a replacement for the original content. If the new content
has different dimensions, then the user agent will reflow the viewport

I need more discussion before rewording 3.2.4. I am not seeing a use-case
for simultaneous rendering of all non-synchronized alternatives. It seemed
very useful when Jan and I proposed it. Useful yes. An accessibility
barrier...I am not sure. 
Jim Allan, Accessibility Coordinator & Webmaster
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315    fax: 512.206.9264  http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964
Received on Tuesday, 18 November 2008 20:05:26 UTC

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