Additions re Structural Navigation

Hi, Silvia:

This took longer than I expected, but I think it's comprehensive. I will
appreciate your help adding this to our document.

There are two parts:

1.	Somewhat long to go into Sec. 2.4. Begin and end points marked
in context.

2.)	A new section for 3.x. Please insert where you think appropriate
(and cross-link as you deem appropriate).

If you see edits, please feel free. It's late here, and I well might
have missed something.

Thanks for your help.


Content Navigation by Content Structure

   Most people are familiar with fast forward and rewind in media content. However, fast forward and rewind, because they
   progress through content based only on time, are ineffective particularly when the content is being used for other than
   entertainment purposes. People with disabilities are also particularly disadvantaged if forced to rely solely on
   time-based forward and rewind to study content.

   Fortunately, most content is structured, and appropriate markup can expose this structure to forward and rewind
   controls:
     * Books generally have chapters and perhaps subsections within those chapters. They also have structures such as page
       numbers, side-bars, tables, footnotes, tables of contents, glossaries, etc.
     * Short music selections tend to have versus and repeating choruses.
     * Larger musical works have movements which are further dividable by component parts such as "Exposition,
       Development, and Recapitulation;" or "Theme and Variations."
     * Operas, theatrical plays, and movies have acts and scenes within those acts.
     * Television programs generally have clear divisions, e.g. newscasts have individual stories usually wrapped within a
       larger structure called "News, Weather, and Sports."
     * A lecturer may first lay out the issue, then consider a series of approaches or illustrative examples, and finally
       the lecturer's conclusion.

/begin insert--

Support for effective structural navigation will require an additional control
not typically available on current media players. This realtime control
will allow the user to adjust the level of granularity applied to "fast
forward" and "rewind," (also called "next" and "previous").

Two Examples of Granularity Levels

1.	In a news broadcast, the most global level (analogous to <h1>) might be "News, Weather, and Sports."
	The second level (analogous to <h2>) would identify each individual news (or sports) story. 

	With the granularity control set to level 1, "next" and "previous"
would cycle among "News, Weather, and Sports." Set at level 2, it would cycle
among individual news (or sports) stories.

2.	In a bilingual "Audiobook Plus Text" production of Dante Alighieri's
*	"La Divina Commedia," the user would choose whether to listen to the
*	original medieval Italian or its modern language translation--possibly
*	toggling between them. Meanwhile, both the original and translated
*	texts might appear on screen, with both the original and translated
*	text highlighted, line by line, in sync with the audio narration.

	The most global (<h1>) level would be each individual "book," "Inferno," "Purgatorio," and "Paradiso." 
	The second (<h2>) level would be each individual "Canto."
	The third (<h3>) level would be each individual "Verso."
	The fourth (<h4>) level would be each individual line of poetry.

With granularity set at level 1, "Next" and "Previous" would cycle among the
three books of "The Divine Comedy." Set at level 2, they would cycle among its
"Cantos," at level 3 among its "Versos," and at level 4 among the individual
lines of poetry text.

Note that, just as printed books may have footnotes, sidebars, and other
ansilary content structures, media productions may also contain ansilary content. Newscasts will have commercials. Audio
productions of "The Divine Comedy" may well include reproductions of famous frescoes or
paintings interspersed throughout the text, though these are not properly part
of the text/content. Structured navigation controls will need to support:

*	Pausing primary content traversal to provide access to such ansilary
*	content in line. This is analogous to Section 2.2 "Extended audio
*	description," and Section 2.6 "Extended Captioning."

*	Skipping ansilary content in order to not interrupt content flow.

*	Direct access to each ansilary content item, including with "next" and
*	"previous" controls, apart from accessing the primary content of the
*	title.

/end insertion--

   Just as the structures introduced particularly by nonfictional titles make books more usable, media is more usable when
   its inherent structure is exposed by markup. And, markup-based access to structure is critical for persons with
   disabilities who possess less ability to infer structure from purely presentational queues.


**New Controls Section**

3.x Granularity Level Control for Structural Navigation

As explained in Section 2.4, a realtime control mechanism is required for
adjusting the granularity of what specific structural navigation point "Next"
and "Previous" controls will access. All identified structures, including
ansilary content as defined in 2.4, must be accessible with the use of "next"
and "Previous," as refined by the granularity control, and possibly as further
refined by a control indicating whether ansilary structures are to be skipped,
played in line, or accessed directly apart from primary content. This control
must be input device agnostic. Producers and authors may optionally provide
additional access options to identified structures, such as direct access to
any node in a Table of Contents.

-- 

Janina Sajka,	Phone:	+1.443.300.2200
		sip:janina@asterisk.rednote.net

Chair, Open Accessibility	janina@a11y.org	
Linux Foundation		http://a11y.org

Chair, Protocols & Formats
Web Accessibility Initiative	http://www.w3.org/wai/pf
World Wide Web Consortium (W3C)

Received on Thursday, 27 May 2010 02:35:25 UTC