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Re: screen readers for macs - also bobby question

From: Jukka K. Korpela <jkorpela@cs.tut.fi>
Date: Wed, 12 Mar 2003 00:41:33 +0200 (EET)
To: w3c-wai-ig@w3.org
Message-ID: <Pine.GSO.4.50.0303120013560.5280-100000@korppi.cs.tut.fi>

On Tue, 11 Mar 2003, Bill LaPlant wrote:

> It seems to me that in providing text descriptions of graphics, we really must
> consider the intent of the content provider in deciding the thoroughness of the
> descriptions.

I guess so, but this is not what alt attributes are about. An alt
attribute is meant to be a replacement for an image, not a description of it.

Unfortunately even the W3C recommendations are partly confused in this
issue. One of the causes of this confusion is probably the fact that in
quite a many cases, it is not _possible_ to write a replacement for an
image into an alt attribute, either due to the technical limitations of
the attribute structure and implementation or due to lack of time and
other resources, or perhaps due to the inherent nature of the image.

I've written a partial explanation of the "great confusion" (alternative
versus description): http://www.cs.tut.fi/~jkorpela/html/alt.html#idea

If you use a picture of Mona Lisa merely as decoration, alt="" is
adequate. If you use it on a page about Leonardo da Vinci, then maybe
alt="Leonardo da Vinci painted Mona Lisa." (or something in a little
more stylish language) would be adequate, if that's what you are trying to
say. If the page is _about_ Mona Lisa and the picture is included so that
the user can look at it while reading the commentary, then obviously there
is no way to write a replacement. What we would really need is a coded way
of saying that the image contains essential visual information that cannot
be expressed in words and a name, or label, for the image so that it might
be associated with something that the user knows otherwise. I have
suggested the use of notations like alt="[Mona Lisa]", in lack of anything
better. The brackets would tell that it's not a replacement but a name, or

> If the image is provided to "dress up" the page, not, therefore
> adding to the substance of the content, then it would seem to me that the briefer
> description would be appropriate for the alt tag.

For what purpose? Why would you tell me that a page contains red bullets
just because you've decided to use red bullets as separators or bullet
points? Wouldn't it then be equally important to tell me, for each and
every list item on the page, that a style sheet has been used to make the
list bullets red (assuming, for the sake of argument, that CSS would let
me do that, as it should)?

> If, on the otherhand, the image
> is illustrative of some key point to be made that amplifies the rest of the content,
> then a more detailed description would be appropriate.

No, a textual equivalent should be given. It should be the text that you
would write if no images existed.

> If the designers are
> enamored of a detailed description of the image used for decorative purposes for
> some reason, in addition to the shorter alt tag, they can always add a "D" link
> which can be by-passed by the reader in a hurry.

No, that would just add annoyance to foolishness. The "D" link concept has
largely been abandoned even in theory, and it was not much used in
practice, but no matter what you use as a link, there should be something
potentially useful at the other side of the link. If an author thinks that
explaining the decorations is somehow relevant, then such things would
belong to the footnote-like stuff at the end of the page, an "about this
page" section. And if there's a link to a document about some decoration,
then it should be clearly identified as such in the link text.

Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
Received on Tuesday, 11 March 2003 17:41:36 UTC

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