The Timed Text Working Group just discussed Constrain ttp:profile's @use attribute (#1029). ttml2#1137.
The full IRC log of that discussion
<nigel> Topic: Constrain ttp:profile's @use attribute (#1029). ttml2#1137
<nigel> github: https://github.com/w3c/ttml2/pull/1137
<cyril> glenn: the PR has been opened for 27 days, I need a review
Closes #1029.