From HTML WG Wiki
Cyclic Header Chains
A concern was raised that cyclic header references may result in an infinite loop. Implementations do not accumulate headers for headers, so although cyclic references should not be considered conforming, cyclic header references do not cause issues with implementations.
Purpose of headers Attribute
The purpose of the attribute is to specify the headers for a particular table cell so that they can be queried by a user or announced to provide context when the user navigates along a particular axis.
How Assistive Technology Works with headers
Assistive technology does not accumulate the headers for all other headers. When the user queries the cell, only the headers pointed to by the headers attribute are announced.
The HTML5 specification should have a conformance requirement stating that cyclic references are illegal.
- Re: function and impacts (was: @scope and @headers reform) - Henri Sivonen