Extended Descriptions
Extended descriptions, like alt text, are text descriptions of visual elements. Unlike alt text, extended descriptions are intended to be longer and are usually written in a separate page. The two most common ways of implementing extended descriptions are using a description or D link or using the long description attribute in an image tag. Both of these methods have pros and cons as description links are more accepted by older screen readers but the long description attribute is seen as more aesthetically pleasing. Future browsers and third-party applications may allow optional access to the long description page.
Example
Extended description using a D-link
HTML code:
<img src="Glycolysis.jpg" alt="Glycolysis
Image">
<a href="glycolysis.html">D</a>
Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. Glycolysis can be carried out anaerobically (in the absence of oxygen) and is thus an especially important pathway for organisms that can ferment sugars. For example, glycolysis is the pathway utilized by yeast to produce the alcohol found in beer. Glycolysis also serves as a source of raw materials for the synthesis of other compounds. For example, 3 phosphoglycerate can be converted into serine, while pyruvate can be aerobically degraded by the Krebs or TCA cycle to produce much larger amounts of ATP.
Extended description using the longdesc attribute
HTML code:
<img src="Glycolysis.jpg" alt="Glycolysis
Image" longdesc="glycolysis.html">
Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. Glycolysis can be carried out anaerobically (in the absence of oxygen) and is thus an especially important pathway for organisms that can ferment sugars. For example, glycolysis is the pathway utilized by yeast to produce the alcohol found in beer. Glycolysis also serves as a source of raw materials for the synthesis of other compounds. For example, 3 phosphoglycerate can be converted into serine, while pyruvate can be aerobically degraded by the Krebs or TCA cycle to produce much larger amounts of ATP.
Links
WAI Web Content
Accessibility Curriculum
(http://www.w3.org/WAI/wcag-curric/sam3-0.htm)
Long Descriptions
(http://www.webaim.org/techniques/images/6)
