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Re: longdesc spec text

From: Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>
Date: Tue, 26 Apr 2011 19:21:22 +0100
Message-ID: <BANLkTinTA3PFsujbYaLdeMbgwfw3Pe36fg@mail.gmail.com>
To: Laura Carlson <laura.lee.carlson@gmail.com>
Cc: Geoff Freed <geoff_freed@wgbh.org>, Jan Richards <jan.richards@utoronto.ca>, W3C WAI-XTECH <wai-xtech@w3.org>, HTMLwg <public-html@w3.org>
On Tue, Apr 26, 2011 at 6:31 PM, Laura Carlson
<laura.lee.carlson@gmail.com> wrote:
> Hi Ben,
>
>> The spec language likely needs to be carefully coordinated with:
>>
>> http://dev.w3.org/html5/spec/links.html#following-hyperlinks
>
> What text would you suggest for for longdesc in the  4.8.1 the img
> element section? I'm open to suggestions.

Hmm. I'd base it on the treatment of @cite here:

http://dev.w3.org/html5/spec/grouping-content.html#the-blockquote-element

So something like:

  The requirements on the alt attribute's value are described in the
next section.

  Some images benefit from a long text alternative that is either too
  long to be included in the main flow of the document or requires
  structured markup that cannot be included in an @alt attribute. Such a
  long text alternative of the image, if it has one, may be referenced in
  the longdesc attribute.

  If the longdesc attribute is present, it must be a /valid URL
  potentially surrounded by spaces/
  (http://dev.w3.org/html5/spec/urls.html#valid-url-potentially-surrounded-by-spaces).

  To obtain the corresponding long text alternative link, the value of
  the attribute must be resolved relative to the element. The link must
  point to either a different document from the image or a /fragment/
  (http://dev.w3.org/html5/spec/history.html#the-indicated-part-of-the-document)
  of the same document that does not contain the image. User agents
  should allow users to access long text alternatives.

  The longdesc IDL attribute must reflect the element's longdesc content
  attribute.

I've preferred Understanding WCAG 2.0's language of "long text alternative"
to "long description". I've also done my best with the problematic
question of how long is too long.

Personally, I'd be wary of saying "User agents should allow users to
access long text alternative" here, but Hixie's draft includes "User agents
should allow users to follow citation links" so I've included it for
consistency. I've tried to phrase so it does not especially encourage
opening a new browser context over inlining content.

The @alt requirements section would probably need a new subsection
describing what the @alt should be when the image also has a
separate long description.

--
Benjamin Hawkes-Lewis
Received on Tuesday, 26 April 2011 18:21:50 UTC

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