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UAWG comments on the HTML5 Image Description Extension

From: Jim Allan <jimallan@tsbvi.edu>
Date: Thu, 23 Jan 2014 17:26:07 -0600
Message-ID: <CA+=z1WmMf7E6d5OS+P8k6KBbuj39VBDs9E_gyGs9K-kjo5aWog@mail.gmail.com>
To: WAI-ua <w3c-wai-ua@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Below are UAWG comments on the HTML5 Image Description Extension
(longdesc) (https://dvcs.w3.org/hg/html-proposals/raw-file/default/longdesc1/longdesc.html).

Important Comments:

1.  Other image types: We don't understand the decision to allow the
new longdesc to apply only to img elements, as it seems to be just as
appropriate for things like groups of images (which may make up one
whole image as far as the user is concerned), svg elements, objects,
and even tables or arrangements of colored divs. We recommend allowing
longdesc to apply to other elements.

2.  Discoverable by users: Section 3.0.03 says 'User agents should
enable users to discover when images in a page contain a long
description. We believe that the spec should make this a requirement
(MUST instead of SHOULD), and also ensure that the user does not need
to try clicking on every element to find which have longdesc
properties.
Suggested wording, "User agents MUST enable users to discover when
images in a page contain a long description without having to query
each element individually.
A similar change should be made in the Requirements section where it
currently says "A user SHOULD be able to determine that there is a
description available for a given image." This should also be changed
from SHOULD to MUST.

3.  Provide UI guidance: The document should provide some guidance or
examples of how user agents could implement linked images with
longdesc. Section 3.0.3 says "If the longdesc value is valid, User
agents must make the link available to all users through the regular
user interface(s)." That's ambiguous as to whether it means "through
the user agent's own UI (rather than relying on assistive technology)"
or "through the user agent's normal clicks and keystrokes for
activating links". It's clear that the user agent can't simply provide
a single standard hyperlink when the img is inside an anchor and also
contains a longdesc unless that pops up a choice of jumps, but it
could instead append a separate hyperlink to the longdesc, or it could
provide a separate command on the link's context menu and/or on a menu
bar menu when the element has focus, etc. Of course, any guidance
should be suggestions, rather than prescriptive, as we don't want to
prevent user agent developers from providing new, innovative UI or UI
that's appropriate for their product and its platform. We also
recommend you explicitly state that the longdesc link be actionable
rather than allowing the user agent to merely display the URI (as is
done by Firefox's View Image Info command in the Context menu for an
image.).

Editorial Comments:

1. Use Case keywords seem random: In the section on Use Cases, the
Requires and Helped By keywords (which link to appropriate entries in
"Requirements for an Image Description Functionality") are a nice
touch. However, we don't understand the choices made as to which
keywords are listed for each use case. For example, why would
Discountability be important for "Identifying a well-known image", but
not for "Describing a complex diagram", or why would Simple Return be
useful for the latter but not the former?

2. Contrast with ARIA DescribedBy: The use case "Referring to an
existing description" sounds like exactly what ARIA DescribedBy is
used for, so it might be good to clarify why longdesc is also needed,
and whether you're recommending one or both be used.

3. Delimit blocks in the document: As a purely editorial/formatting
issue, the document should not convey information by using CSS :before
pseudo elements or graphical formatting alone. The problem with
:before is the content is not in the DOM and screenreaders don't see
it. The problem with graphical formatting is that the blocks starting
with "This section is informative" are indented and have a differently
colored background, but there is nothing textual to denote where the
block ends.

4. Web page contains insecure content: FYI, when loading the page
https://dvcs.w3.org/hg/html-proposals/raw-file/default/longdesc1/longdesc.html,
Firefox 26.0 generates a warning saying "Firefox has blocked content
that isn't secure. Most websites will still work properly even when
this content is blocked." It links to the following page for details:
https://support.mozilla.org/en-US/kb/how-does-content-isnt-secure-affect-my-safety.

5. Under the requirement "Structured Markup" is "A user should be able
to determine that there is a description available for a given image."
This is not really related to structured markup, so should be under
the requirement "Discoverability". We suggest moving "A user should be
able to determine that there is a description available for a given
image. " in the definition of Structured Markup to the definition

Thank-you
User Agent Working Group
Jim Allan, Kelly Ford Co-Chairs
Jeanne Spellman, Team Contact

-- 
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 Thursday, 23 January 2014 23:26:31 UTC

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