ACTION 72: @headers rewrite

This document is the deliverable for Issue Tracker ACTION 72, which is bound to ISSUE 57.

Rationale for Changing the Spec

• The constraint that the headers attribute can only reference the id attribute value of a header cell is of very little use, and makes it impossible to define most complex data tables accessibly.
• A mechanism to associate data cells with conceptual header cells and pure headings is required to determine content relationships.
• For further rationale and history of this issue consult the #head-904bf8616cfa7da91460880d4e86b4c4cf7ea0ea reference section below.

Recommendation

Extend the definition of the headers attribute to allow it to reference a td. This would make it possible for complex data tables to be marked up accessibly.

Only pure headings should be marked up with th, and data cells should be marked up with td. When a cell contains data but acts as a heading, the cell should be marked up with a td, and is a conceptual header cell. In this situation, the headers attribute should be able to reference the id attribute value of the conceptual header cell marked up with a td, as well as any corresponding pure header cells marked up with a th.

Original Text

"...The headers attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens, each of which must have the value of an ID of a th element..."

Source: 3.13 Tabular data (headers)

New Proposed Text

"...The headers attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens, each of which must have the value of an ID of a th or td element..."

References

• Bug 5822: The headers attribute should be able to reference a td - Reported by Gez Lemon.
  • Example data table is reasonably simple, and there should be a way of marking it up so that the headers can be queried by a non-visual user agent.
  • Testing (Bug 5822) - Findings: The headers/id mechanism provides needed functionality.
• headers attribute issue - Thorough details and history from May 2007 to date include:
  • Issue Definition
  • Status: Open - Issue isn't solved by the current spec. It also circumvents PF's advice.
  • Proposed Two Step Solution - This @headers rewrite is Step 1.
  • HTML WG Actions, Responses, Bug Reports
  • Rationale - Previously discussed reasoning for including the headers attribute. May 2007 to date.
  • Advice Request to PFWG and their Response
  • Advice From Other Accessibility Authorities
  • Research
  • Examples
  • Use Cases
  • Policies, Guidelines, and Law
  • Related Blog Posts and References
  • Related IRC Discussion and IRC Teleconference Minutes
  • Related E-mail Threads