W3C home > Mailing lists > Public > public-html-a11y@w3.org > September 2010

[Bug 10455] Mint a describedby attribute for the img element

From: <bugzilla@jessica.w3.org>
Date: Thu, 02 Sep 2010 20:30:55 +0000
To: public-html-a11y@w3.org
Message-Id: <E1OrGQx-0001Fj-1n@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10455





--- Comment #70 from Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>  2010-09-02 20:30:52 ---
(In reply to comment #67)
> supporting author ignorance by simply telling them "copy-and-paste" this markup
> into your content if X equals Y is a HORRENDOUS idea -- the point of native
> semantics is to be easily understood and implemented by developers and authors
> alike -- telling authors to use pre-canned snippets of HTML+RDFa is a complete
> non-starter -- HTML should NOT be encouraging authors to copy-and-paste
> snippets of code without the author/content creator understanding how that code
> works, how it is expressed by a UA or assistive technology, and how to tailor
> that code to the content creator's needs...

> supporting author ignorance by simply telling them "copy-and-paste" this
> markup into your content if X equals Y is a HORRENDOUS idea -- the point of
> native semantics is to be easily understood and implemented by developers and
> authors alike -- telling authors to use pre-canned snippets of HTML+RDFa is
> a complete non-starter -- HTML should NOT be encouraging authors to
> copy-and-paste snippets of code without the author/content creator
> understanding how that code works, how it is expressed by a UA or assistive
> technology, and how to tailor that code to the content creator's needs...

Authors operate at varying levels of abstraction.

It seems to me that most authors operate at a high level of (doubtless highly
leaky) abstraction and don't understand how HTML "works" beyond the level of
inserting "a", "b" and "i" tags and expecting the browser to link and render
the text accordingly.

If you literally tell authors to copy and paste code with no explanation
whatsoever, then of course they will fail. If you tell them what parts of the
code they need to change and why, they may well achieve their goal (in this
case, associating images with long descriptions) without understanding every
detail of how it works (in this case, how bytes are converted into characters
which are parsed into a DOM, from which N-triples are extracted, some of which
are selected to be mapped into MSAA in the "accDescription" field, on the
basis of which JAWS will notify the user a long description is present and
allow the user to open the long description in a new window).

For example, you could give authors a hidden long description recipe as
follows:

   - Create a separate HTML page containing your long description.  Identify
     your "img" element with a unique "id" attribute (e.g. "my-image")
   - Put an empty "span" element beside it to hold machine-readable information
     about how to locate the long description.
   - Set the "resource" attribute of the "span" to the URL of the long
   - description.  Set the "about" attribute of the "span" to reference the
   - "img" element (not the image source) by fragment URL by putting a hash
     sign before the "id" value (e.g. "#my-image").
   - Set the "rel" attribute of the span to "longdesc" to indicate the resource
     is a long description for the subject of the "about" attribute (i.e. the
     "img" element).

Note how the Facebook Open Graph documentation does not attempt to explain to
authors the mysteries of how the Open Graph annotations are converted to
N-triples, and concentrates on explaining to authors what the various
properties mean.

Given WG opposition to retaining "longdesc" and given uncertainty about the
direction ARIA will take, I'm trying to assess Laura's assertion that "HTML5
fails to adequately provide" Requirements 1-6 by looking at whether HTML5 and
sister technologies (specifically ARIA and HTML+RDFa) can meet these
requirements or not. It seems to me that while these technologies do not (and I
would argue should not) mandate user interface, they can be used to express the
semantics of associating a long description with an image and enable the
building of user interfaces meeting the stated requirements. (At any rate,
nobody has demonstrated that they cannot.)

I do not dispute that simpler features are preferable, and will see higher
adoption.

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Received on Thursday, 2 September 2010 20:30:56 UTC

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