SIA-R46All table header cells have assigned data cells

Accessibility requirements

This rule tests conformance of the following accessibility requirements:

1.3.1 Info and Relationships

Description

This rule checks that each table header has assigned data cells in a table element.

Applicability

This rule applies to every <th> element in the HTML namespace for which all the following are true:

the element has a semantic role of rowheader or columnheader; and
the element is visible; and
the element is included in the accessibility tree; and
the element has at least one ancestor in the flat tree which is a <table> element; and
the element's closest <table> ancestor is included in the accessibility tree.

Expectations

The target element is assigned to at least one element with a semantic role of cell or inheriting from cell.

Assumptions

This rule makes the following assumption:

Table header cells have a relationship conveyed through presentation with other cells within the same table.

Accessibility support

This rule has the following accessibility support concern:

Table markup and header cell association is not well supported by some popular assistive technologies.

Examples

Implementation Details

When deciding whether a <th> whose scope attribute is in the auto state is a column header or row header, empty data cells are ignored by this rule. This in turn impacts header assignment, since these cells may now be assigned as headers. Most User Agents and Assistive Technologies likewise ignore empty data cells. It is a common practice to have an empty data cell in the top-left corner of tables with both columns and rows headers.