Remarks

The long description is a non-visual element used by systems such as pronouncing screen readers to make the object accessible to people or systems that cannot read/see/display the object.

This element was originally designed to contain a description, but some newer systems expect this element to contain a URI that points to such a description. In the current Tag Sets, this will mean a textual URI, untagged.

Accessibility: Please reserve this tag for accessibility uses such as pronouncing screen readers. The <long-desc> is not a visual element; rather, its purpose is to be spoken in circumstances where the visual form of the object cannot be viewed. This element differs from the <alt-text> element in both length and purpose. The <alt-text> is typically very short, for quick scan reading by a screen reader or showing as words behind a graphic. The <long-desc> is meant for an extended description of an object such as a figure, table, graphic, etc., for example, a textual summary of a pie chart that explains both the visual form of the chart and significance of its findings.

Best Practice: The <long-desc> element should not to be used as a replacement for <caption>, which is a visual element that is typically displayed alongside a figure, table, etc. Thus <long-desc> should not be used to hold supplementary data. The <long-desc> is not a visual element.

<!ELEMENT  long-desc    (#PCDATA %long-desc-elements;)*              >

               
...
<table-wrap>
<caption>
<title>The Size/Price Paradox</title>
</caption>
<long-desc>Table is a price comparison of some
unknown objects that are identified only by
color as Red and Green. The price of small,
medium, and large objects is given for each
color, with Green objects getting cheaper with
increasing size, from $3.25 for small to $2.25
for medium to $1.15 for large. In contrast, Red
objects get more expensive with size, with small
costing $3.25, medium for $5.25, and large for $9.95.
</long-desc>
<table rules="rows">
<thead>
<tr>
<th>Color</th>
<th>Size</th>
<th>Price</th>
</tr>
</thead>
<tbody>
<tr>
<td rowspan="3">Green</td>
<td>small</td>
<td>$3.25</td>
</tr>
<tr>
<td>medium</td>
<td>$2.25</td>
</tr>

<tr>
<td>large</td>
<td>$1.15</td>
</tr>

<tr>
<td rowspan="3">Red</td>
<td>small</td>
<td>$3.25</td>
</tr>

<tr>
<td>medium</td>
<td>$5.25</td>
</tr>

<tr>
<td>large</td>
<td>$9.95</td>
</tr>
</tbody>
</table>
</table-wrap>
...