Where ARIA attribute values are impacted by IDL attributes, it's more accurate to reference the source of the value/state (e.g., content attribute, CSS pseudo-class) rather than the IDL attribute. For example, rather than reference the validity IDL attribute, aria-invalid's value should be correlated with the :invalid CSS pseudo-class which validity reflects (related comment: w3c/aria#2223 (comment)).

There are two instances in html-aam that reference the indeterminate IDL attribute that should have language updated to use the :indeterminate CSS pseudo-class rather than indeterminate IDL attribute:

• https://w3c.github.io/html-aam/#att-indeterminate
• https://w3c.github.io/html-aam/#el-input-checkbox