This document is a draft, and is designed to show changes from a previous version. It is presently showing added text,changed text,deleted text,[start]/[end] markers,and Issue Numbers.
Changes are displayed as follows:
HTML 4.01, XHTML 1.x
This technique relates to:
The objective of this technique is to provide a brief overview of how a data table is organized or a brief explanation of how to navigate the table. The summary attribute of the table element makes this information available to people who use screen readers; the information is not displayed visually.
The summary is useful when the table has a complex structure (for example, when there are several sets of row or column headers, or when there are multiple groups of columns or rows). The summary may also be helpful for simple data tables that contain many columns or rows of data.
The summary attribute may be used whether or not the table includes a caption element. If both are used, the summary should not duplicate the caption.
Although WCAG 2 does not prohibit the use of layout tables, CSS-based layouts are recommended in order to retain the defined semantic meaning of the HTML table elements and to conform to the coding practice of separating presentation from content. However, if a layout table is used, then the summary attribute is not used or is null.
The purpose of a layout table is simply to control the placement of content; the table itself is “transparent" to the user. A summary would “break" this transparency by calling attention to the table. A null summary (summary="") on layout tables is acceptable.
This example shows a bus schedule. The route number and direction are included in the summary along with information on how to use the schedule.
<table summary="Schedule for Route 7 going downtown. Service begins at 4:00 AM and ends at midnight. Intersections are listed in the top row. Find the intersection closest to your starting point or destination, then read down that column to find out what time the bus leaves that intersection."> <tr> <th scope="col">State & First</th> <th scope="col">State & Sixth</th> <th scope="col">State & Fifteenth</th> <th scope="col">Fifteenth & Morrison</th> </tr> <td>4:00</td> <td>4:05</td> <td>4:11</td> <td>4:19</td> </tr> … </table>
In this example both a summary attribute and a caption element are used. The caption identifies the bus route. The summary helps users who are blind understand how to use the schedule. Screen readers read the caption, followed by the summary.
<table summary="Intersections are listed in row 1. Find the intersection closest to your starting point or destination, then read down that column to find out what time the bus leaves that intersection. Service begins at 4:00 AM and ends at midnight."> <caption>Route 7 Downtown (Weekdays)</caption> … </table>
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HTML 4.01 summary attribute
Check for layout tables: determine whether the content has a relationship with other content in both its column and its row.
If “no," the table is a layout table.
If “yes," the table is a data table.
If the table is a layout table, check that the summary attribute is not present or summary attribute is null.
If the table is a data table and a summary is present, check that the summary attribute describes the table's organization or explains how to use the table
If both a summary attribute and a caption element are present for this data table, check that the summary does not duplicate the caption.
For layout tables, #2 is true.
For data tables, #3 and #4 are true.