- From: poot <cvsmail@w3.org>
- Date: Mon, 10 May 2010 23:35:28 +0900 (JST)
- To: public-html-diffs@w3.org
steve: started on section 11 When a text alternative is unknown at the
time of publication
http://dev.w3.org/cvsweb/html5/alt-techniques/Overview.html?r1=1.22&r2=1.23&f=h
===================================================================
RCS file: /sources/public/html5/alt-techniques/Overview.html,v
retrieving revision 1.22
retrieving revision 1.23
diff -u -d -r1.22 -r1.23
--- Overview.html 5 May 2010 15:06:17 -0000 1.22
+++ Overview.html 10 May 2010 14:35:09 -0000 1.23
@@ -257,7 +257,12 @@
</li>
<li><a href="#methods">Methods for Providing Text Alternatives</a>
<ul>
- <li><a href="#altmethod">The img element alt attribute</a></li>
+ <li><a href="#altmethod">The img element alt attribute</a>
+ <ul>
+ <li>Using an empty alt attribute</li>
+ <li>What length should a text alternative be</li>
+ </ul>
+ </li>
<li>The figure and figcaption elements</li>
<li>The aria-labelledby and aria-describedby attributes</li>
<li>Linked text content within the same document or another document</li>
@@ -278,12 +283,12 @@
<li><a href="#icons">8. Icons and logos</a></li>
<li><a href="#pictures">9. Images of Pictures</a></li>
<li><a href="#webcam">10. Webcam images</a></li>
- <li>11</li>
- <li>12</li>
- <li>13. <a href="#captcha">CAPTCHA images</a></li>
- <li><a href="#glossary">Glossary</a></li>
+ <li><a href="#imgslices">11. A group of images that form a single larger picture with and without links</a></li>
+ <li><a href="#unknown">12. When a text alterntive is unknown at the time of publication</a></li>
+ <li><a href="#captcha">13. CAPTCHA images</a></li>
</ul>
</li>
+ <li><a href="#glossary">Glossary</a></li>
</ul>
<h2 id="intro">Introduction</h2>
<H3 id="text-alt">Text Alternatives</H3>
@@ -330,8 +335,10 @@
<li>If the alt attribute content is too long it may cause reading issues in some assistive technologies.</li>
<li>Semantic structure cannot be added to alt attribute content.</li>
</ul>
+<h6>Using an empty <code>alt</code> attribute <code>alt=""</code></h6>
<h6>How long should a short text alternative be?</h6>
<p>The answer to this question very much depends on the context an image is being used in. While there are no definitive right or wrong lengths for text alternatives provided using the <code>img</code> elements <code>alt</code> attribute, the general consensus is that if the text alternative is longer than 75-100 characters (1 to 2 sentences), it should not be considered a short text alternative and should not be presented using the <code>alt </code>attribute.</p>
+<h3> </h3>
<h3>The <code>figure</code> and <code>figcaption</code> elements</h3>
<p><span class="note">to do</span></p>
<h5>Advantages:</h5>
@@ -1012,7 +1019,7 @@
<LI><A href="http://dev.w3.org/html5/markup/figcaption.html">The HTML5 figcaption element</A></LI>
</ul>
<p> </p>
-<h3>11. A group of images that form a single larger picture with and without links</h3>
+<h3 id="imgslices">11. A group of images that form a single larger picture with and without links</h3>
<p>When a picture has been sliced into smaller image files that are then displayed together to form the complete picture again, one of the images MUST have its alt attribute set as per the relevant rules that would be appropriate for the picture as a whole, and then all the remaining images MUST have an empty alt attribute.</p>
<h4>Example 11.1</h4>
<div class="example">
@@ -1041,8 +1048,8 @@
</pre>
</div>
<p> </p>
-<h3>12. Images that are a key part of the content</h3>
-<p><span class="note">to do</span></p>
+<h3>12. When a text alternative is unknown at the time of publication</h3>
+<p>In some cases an image may be included in a published document, but the author is unable to provide an appropriate text alternative. In such cases the minimum conformance requirement is to provide a caption for the image. The caption SHOULD be provided using either the <code>figcaption</code> element. The use of <code>figcaption</code> is recommended over the use of the <code>alt</code> attribute as the <code>figcaption</code> element is designed as a container for caption text, while the alt attribute is designed as a container for a text alternative. In practice the alt attribute has and will continue to provide a more generic method for providing information about an image until such times that the <code>figcaption</code> element is well supported in browsers and assistive technologies.</p>
<H3 id="captcha">13. CAPTCHA Images </H3>
<p><A title="http://www.w3.org/TR/WCAG20/#CAPTCHAdef" href="http://www.w3.org/TR/WCAG20/#CAPTCHAdef">CAPTCHA</A> stands for "Completely Automated Public Turing test to tell Computers and Humans Apart". CAPTCHA images are used for security purposes to confirm that <A title="http://www.w3.org/TR/WCAG20/#contentdef" href="http://www.w3.org/TR/WCAG20/#contentdef">content</A> is being accessed by a person rather than a computer. This authentication is done through visual verification of an image. CAPTCHA typically presents an image with characters or words in it that the user is to re-type. The image is usually distorted and has some noise applied to it to make the characters difficult to read. </p>
<p>Provide <A title="http://www.w3.org/TR/WCAG20/#text-altdef" href="http://www.w3.org/TR/WCAG20/#text-altdef">text alternatives</A> that identify and describe the purpose of the <A title="http://www.w3.org/TR/WCAG20/#non-text-contentdef" href="http://www.w3.org/TR/WCAG20/#non-text-contentdef">non-text content</A>, and provide alternative forms of the CAPTCHA using output modes for different types of sensory perception. For instance provide an audio alternative along with the visual image. Locate the audio option right next to the visual one. This helps but is still problematic for people without sound cards, the deaf-blind, and some low hearing people. Another method is to include a form that asks a question along with the visual image. This helps but is can be problematic for people with cognitive impairments. </p>
Received on Monday, 10 May 2010 14:36:02 UTC