- From: <bugzilla@jessica.w3.org>
- Date: Sat, 17 Sep 2011 05:12:09 +0000
- To: public-html-a11y@w3.org
http://www.w3.org/Bugs/Public/show_bug.cgi?id=14150
theimp@iinet.net.au changed:
What |Removed |Added
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CC| |theimp@iinet.net.au
--- Comment #3 from theimp@iinet.net.au 2011-09-17 05:12:04 UTC ---
Alt is for Alternative. By definition, it's intended for when the image is not
used (e.g. not viewed by a user, or not analyzed by a search engine).
Alt is not for general-purpose metadata, such as search engine hooks or
authorship information.
Text that is needed in the alt tag - text describing the image - is not needed
by those who can see the image. Text that other users need, such as discussion
of the image, or attributes of the image like the date it was created, and so
on, should not be in the alt text.
In some very particular cases, you can have a little bit of overlap; but
usually, the information is distinct.
> <img class="thumbnail" alt="David Kyles" title="David Kyles Shock and Awe"
src="http://files.casuals.us/ybp/2011/1-29/Small/DSC_4320.JPG" />
A better alternative for a gallery:
<img class="thumbnail"
alt="David Kyles, Professional Basketballer for the Wichita State Shockers,
taking a shot from three-point range during the 2011 final against the Alabama
Crimson Tide"
title="Shock and Awe"
src="http://files.casuals.us/ybp/2011/1-29/Small/DSC_4320.JPG" />
This is better because it describes what is important about the image when it
can't be seen. Presumably, anyone seeing the image will know what's important
about it, because the author doesn't think that they need to be told.
However, if there was an associated paragraph afterwards (that is, if all users
would benefit from the text), then what is a useful alternative would change;
for example:
<h1>“Shock and Awe”</h1>
<figure>
<img class="thumbnail"
alt="Profile color photo of David Kyles shooting a basketball"
title="“Shock and Awe” by $photographer"
src="http://files.casuals.us/ybp/2011/1-29/Small/DSC_4320.JPG" />
<figcaption>David Kyles, Professional Basketballer for the Wichita State
Shockers, taking a shot from three-point range during the 2011 final against
the Alabama Crimson Tide.</figcaption>
</figure>
Less detail about the relevance of the photo (i.e. why it is important to the
context of the page), and more about the details of the style of the photo
(i.e. what qualities make distinguish it from other similar images), are more
appropriate now, because the alt attribute only needs to describe details that
are alternative to the photo; other details are explained in the text, and
therefore are not to be duplicated in the alt attribute because they are no
longer alternative.
In some circumstances, a particularly detailed caption might render the image
(particularly a data-heavy and stylistically-minimal image, such as a chart)
merely decorative: and in this case, even a completely blank alt might be
appropriate, though this would be a limited case.
Just like the image itself, what is an alternative depends on the context of
the placement in, and other content of, the document.
If even more specificity is needed, then that really needs to be solved with
microdata/metadata formats such as RDF.
The issue of how search engines uses the alt vs title attribute is a search
engine issue, not an HTML issue.
Even though that may concern you, consider that, as the new markup (such as
figure and figcaption) in HTML5 becomes better used by authors, it will be
easier for search engines to consider them in their algorithms in the near
future.
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Received on Saturday, 17 September 2011 05:12:12 UTC