TAG Horizontal review of TTML2

This morning I was invited to attend TAG who were meeting in London, to discuss TTML2 as part of the horizontal review.

The draft (in progress) minutes are at https://pad.w3ctag.org/p/2017-07-26-minutes.md and will be finalised on https://github.com/w3ctag/meetings/tree/gh-pages/2017/07-london at some point in the future (they will be "day 2").

Here's my unofficial broad summary of the discussion and the conclusions:

  *   TAG considers that CSS is the future for styling and recommends that where possible TTML styling attributes define their semantics on the equivalent CSS properties, potentially alongside the XSL-FO semantics if they are the same, or I guess at least highlight the differences if they exist. The view is that one day, we will have to, so it is cheaper to do it now than later.
  *   I explained a little of the history why TTML references XSL-FO.
  *   I explained that I do not think that TTWG is concerned about syntactic differences, but semantic differences are a potential problem.
  *   There's a possibility that CSS semantics currently aligned with XSL-FO might in the future diverge.
  *   CSS whitespace handling is being looked at actively – we're not the only ones to have problems with it.
  *   It is deemed acceptable to move a spec to Rec if it normatively references other specs that are in Candidate Rec.
  *   CSS publishes roughly annually a snapshot of the current specs that are considered to be stable. This could be used as the basis for any references.
  *   There was a bit of discussion about the basis in XML and XML's future, with no conclusion.
  *   There was some question of whether TTML is the best place to put stereoscopic disparity of text; I argued strongly that it has to be in there if it is to be useful.
  *   Regarding TextTrackCue not being instantiatable directly in most browsers, the suggestion is to discuss with HTML WG and possibly raise issues against individual browser implementations.
  *   TAG agrees that the styling features/requirements of subtitles and captions need to be in CSS.
  *   There's a CSS WG face to face meeting in Paris next week – if possible I will join remotely for the agenda item on TTML2 HR and request to begin work on meeting subtitle and caption presentation requirements in CSS, prior to following up at our meeting in TPAC later in the year (to which I will invite CSSWG as previously agreed).

Kind regards,

Nigel




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