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[Bug 13461] Commentary on Issue #30 (longdesc) from the Association of American Publishers

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Date: Sat, 30 Jul 2011 21:22:30 +0000
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Philippe Le Hegaret <plh@w3.org> changed:

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--- Comment #4 from Philippe Le Hegaret <plh@w3.org> 2011-07-30 21:22:27 UTC ---
Here is a text version of attachment in Comment 1:

The longdesc HTML Attribute & Educational Publishing

As educational publishing companies increasingly offer content in
digital formats, accessibility mechanisms that support complex
instructional materials become increasingly important. The Association
of American Publishers submits this comment regarding the HTML 5 May 25
2011 Working Draft <http://www.w3.org/TR/2011/WD-html5-20110525/>, Issue
30 <http://dev.w3.org/html5/status/issue-status.html#ISSUE-030>
(longdesc) in the hope that the longdesc attribute, or some mechanism
that provides the same benefits, will be available in HTML Version 5 and

About the Association of American Publishers

The Association of American Publishers is the national trade association
of the U.S. book publishing industry. AAP’s more than 300 members
include most of the major commercial publishers in the United States, as
well as smaller and non-profit publishers, university presses and
scholarly societies—small and large. AAP members publish hardcover and
paperback books in every field, educational materials for the
elementary, secondary, postsecondary, and professional markets,
scholarly journals, computer software, and electronic products and services.

Text Alternatives in Educational Publishing: Technology Requirements

Most images on the Web can be made accessible with about 25 or fewer
words <#ftn1> of plain text. In HTML, the alt attribute makes this

Instructional materials often use complex images (including photos,
graphics, diagrams, and maps) to illustrate concepts. For example, an
image may provide a real-world instance of a concept, which may make an
abstract discussion clearer to students. In such cases, students and
instructors with visual impairments need access to the same information.

Twenty-five or fewer words of plain text are not always sufficient to
convey the meaning of such visual content. Conveying information
effectively may not only involve more text but often requires some
combination of headings, nested lists, and data tables. In this
document, we refer to this as ‘structured text.’ The benefits of
structured text for image descriptions were shown in a study conducted
by the National Center for Accessible Media, WGBH
<http://ncam.wgbh.org/experience_learn/educational_media/stemdx>. Refer
to this study for examples. Structured text allows a screen reader user
to choose navigation paths through data, much as a user who can see the
image might follow various paths visually while analyzing an image.
Structured text also gives us the opportunity to use discipline-specific
markup, such as MathML when, for example, parts of an image are labeled
with math notation. Headings allow labeling and dividing text into
shorter segments, to help students understand the schema for a specific
area of knowledge. Semantic tagging also allows users with screen
readers to move more quickly through material if they choose. And, once
the W3C’s WAI-ARIA specification <http://www.w3.org/WAI/intro/aria> is
further implemented, aria-flowto will provide another structure for
representing flow charts and decision trees in structured text.

Use of structured text as a text alternative for an image is supported
in HTML through the longdesc attribute. Though there are other options
for presenting structured-text, the longdesc attribute provides
following benefits:

 For User Experience

  * The longdesc attribute is a dedicated mechanism for just this
    purpose, and it always works in the same way:  
      o Students and instructors will find the same user interface
        throughout all materials, so they will not need to learn new
        interfaces product-to-product, which takes time and attention
        away from the learning content. 
      o The longdesc attribute can be revealed programmatically through
        browser extensions, providing access for users who do not use
        screen readers. Many users benefit from text alternatives,
        especially users with low vision.  
      o The longdesc attribute does not impact the visual design. So,
        authors do not have to worry about how the text might impact the
        visual user experience. Authors can, therefore, focus on the
        experience of students and instructors with visual impairment
        while they write text alternatives. This focus on the primary
        audience helps authors create text that is well-suited for its

 For Production Processes and Quality Assurance:

  * The longdesc attribute is easy to code. There is no need for custom

  * The longdesc attribute works with assistive technology today. If the
    longdesc attribute continues to be supported, content that works
    well for users today can be used in future products without editing.  

  * The longdesc attribute can be programmatically recognized and
    tracked, allowing publishers to locate existing long descriptions
    and to test for the presence of long descriptions. 

We are using longdesc increasingly in our products. Unless a different
mechanism is created that meets all these requirements, we urge the W3C
to keep the longdesc attribute in HTML specifications moving forward.

We do acknowledge that user agent support for the longdesc attribute
should be improved. In particular, users who have low vision or who find
image descriptions helpful for any reason should be able to set their
user agent to reveal the descriptions. The HTML 5 specification should
clarify that user agents should provide this functionality in addition
to passing information to assistive technologies. In this case,
publisher documentation for products with numerous longdesc attributes
might include tips about use of these user agent settings.

Evaluating Other Solutions

We discuss the aria-describedby attribute following to illustrate that
solutions that at first seem to duplicate the qualities of the longdesc
attribute may not actually be as useful when implemented.

The aria-describedby attribute takes the unique indentifier (“ID”) of
another object on the same page as its value. In other words, it points
to another object (e.g. a paragraph or a link) on the page. This
attribute could become an effective way for developers to indicate that
the information provided by an image is actually redundant with other
information on the page.

Screen reader developers might implement this attribute so that it is
silent in screen readers when used on an image by default. They might
also allow those who want additional information to set their screen
reader to announce aria-describedby and to provide a way to jump to the
object indicated by the attribute. An instructor, for example, might
choose this setting to be aware of what sighted students will be

But, the aria-describedby attribute falls short as a mechanism to link
to a separate page of structured text. The aria-describedby attribute
could point to a link on the same page as the image, but:

  * Hiding the link visually would require custom CSS or scripting. The
    mechanism for hiding the link would therefore differ
    product-to-product, making browser extensions or features to show
    the links more complex to code and less reliable for users.  

  * The link would have to be present on the page for screen reader
    users, creating redundancy for those users. 

  * Since the aria-describedby attribute points to a link or to other
    content on the same page, its structure implies a two-step process
    to reach the text alternative. Compared with longdesc, the two step
    process is more tedious: 
     1. The user moves to the object that aria-describedby references. 
     2. If the object is or contains a link or a button, the user
        interacts with that object to move to the text alternative. 

If the issues above are resolved and aria-describedby is used as a way
to access descriptions that are otherwise hidden from all users
(including screen reader users), another problem emerges. In that case,
aria-describedby cannot be silent by default in screen readers when used
on images, compromising its use to illustrate that the content of an
image is already available on the page. Developers may not realize the
distracting and frustratingly circular user experience that this would
cause and might use aria-describedby to point to, for example, a
paragraph just above the image. Users would then likely follow the
aria-describedby announcement, expecting to find additional content, but
they would arrive, instead, at a paragraph that they have likely just read.

We urge the W3C HTML Working Group to write out the expected
implementation and user experience details of any proposed replacements
for the longdesc attribute to be sure that they will be at least as
effective as the longdesc attribute in practice.

<#ftn1> Educational publishers often localize materials, and
different languages have different average word lengths. We also want to
encourage use of vocabulary from the main text in our text alternatives.
So, we find word count more useful as a measure of text alternative
length than character count.

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Received on Saturday, 30 July 2011 21:22:32 UTC

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