Otherwise, if the current node's native markup provides an attribute (e.g. title) or element (e.g. HTML label) that defines a text alternative, return that alternative in the form of a flat string as defined by the host language, unless the element is marked as presentational (role="presentation" or role="none").

In my opinion, the following problems arise here:

• there is no statement what is with implicit role=presentation (example 3, 4).
• there is no statement whether the role=presentation must be at the current node or at the "element that defines a text alternative" for the exception to apply (example 2. 3)
• there is no statement what happens if the element has role=presentation but the role=presentation itself is ignored because of the many exceptions (example 1)

This is problematic because this is currently interpreted differently by browsers and AccName Prototype Test (see the examples)