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@carmacleod, The img role has name from author, so there are only two ways to provide an accessible label, aria-label and aria-labelledby. Referencing the name calculation is like throwing the reader into a rabbit hole. We do not do that elsewhere.

Here is what we have in the dialog role:

Authors SHOULD provide a dialog label, which can be done with the aria-label or aria-labelledby attribute.

From the figure role:

Authors MAY provide a label using aria-label or MAY reference text serving as a label using aria-labelledby.

From the region role:

Authors MUST give each element with role region a brief label that describes the purpose of the content in the region. Authors SHOULD reference a visible label with aria-labelledby if a visible label is present. Authors SHOULD include the label inside of a heading whenever possible. The heading MAY be an instance of the standard host language heading element or an instance of an element with role heading.

For this PR, I propose:

In order for elements with a role of img to be perceivable, authors MUST provide a label, which can be done with the aria-label or aria-labelledby attribute.

This is slightly different from what I proposed in today's meeting. @jnurthen, @a11ydoer, do you concur?