Describe the change

As of ARIA 1.3, aria-hidden="false" will be a synonym of aria-hidden="undefined". However, I noticed that the "undefined" value is now differently defined for various states and properties, e.g.,:

• aria-checked="undefined" means that "The element does not support being checked."; similarly, aria-pressed="undefined" means that "The element does not support being pressed."
• aria-expanded="undefined" means that "The element does not own or control a grouping element that is expandable."
• aria-orientation="undefined" means that "The element's orientation is unknown/ambiguous."

For aria-hidden="undefined", it equates to "The element's hidden state is determined by the user agent based on whether it is rendered."

With the changes to aria-hidden, should we update section 6.2.4 Value and provide a broad definition of what "undefined" means, or perhaps note that it is property-dependent? The current definition of "undefined" does not appear to encompass the full breadth of what this value means:

true/false/undefined
Value representing true, false, or undefined (not applicable). The default value for this value type is undefined unless otherwise specified. For example, an element with aria-expanded set to false is not currently expanded; an element with aria-expanded set to undefined is not expandable.

Link to the version of the specification or documentation you were looking at

Link to documentation: https://w3c.github.io/aria/

Does the issue exists in the editors draft (the editors draft is the most recent draft of the specification)?

Yes