Re: Objections to TPAC resolutions on IMSC1.1

On Mon, Nov 27, 2017 at 11:03 AM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> Hi Nigel et al.,
>
> I do not believe it is possible to fully capture the interactive and
> in-person discussions that led to the consensus resolution adopted at
> TPAC. Nevertheless, based on my notes, below is additional information
> that was shared by at least one member (not necessarily me) during
> these discussions:
>
> - for any IMSC 1.0.1 extension adopted by TTML2, semantics and syntax
> should be modified as little as possible to avoid additional testing,
> training and unintended divergence
>

We are not considering the adoption of non-TTML features in TTML2. We are
defining core functionality that we have been discussing for some time now,
before the creation of either IMSC1 or IMSC1.0.1. Nevertheless, there is a
general agreement that common features should have similar semantics.


>
> - given the objective of aligning TTML and CSS, TTML2 can delay
> adoption of features in its namespace for which there is no CSS
> equivalent but for which industry extensions exist, e.g.
> ebutts:linePadding,
>

Given that such an addition to CSS would require years to obtain in a REC,
it is entirely impractical to use this rationale with TTML2 (and probably
TTML3).


>
> - organizations that have recently adopted IMSC1 might lose confidence
> with the TTWG process if IMSC 1.1 deprecates all IMSC1 extensions and
> replaces them with substantially different alternatives
>

But this has been the plan all along, so such organizations are either
misinformed or not following the work of the TTWG.


>
> - IMSC1 has been adopted and deployed for interchange between multiple
> parties, whereas TTML2 has not
>

False.


>
> - working with EBU to integrate features such as ebutts:multiRowAlign
> in TTML2 is an opportunity to coordinate with an important adopter of
> TTML, and reduce the potential for divergence.
>

Adopting non-TTML vocabulary is contrary to the original requirements
documented by TTAF1 for use in TTML.


>
> > Given that I cannot recall any formal objection to the synonym/alias
> > proposal requested by Netflix,
>
> There was no opportunity to raise formal objections during the TPAC
> meeting since the resolution was adopted by consensus.
>

Any resolution is subject to a period of at least two weeks to obtain
confirmation from member organizations.


>
> Best,
>
> -- Pierre
>
> On Fri, Nov 24, 2017 at 9:13 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>
> wrote:
> > All,
> >
> > This is a situation in which we do not currently seem to have consensus.
> It
> > appears that two camps exist, with mutually incompatible visions for how
> the
> > IMSC 1.1 and TTML2 specifications should incorporate some features.
> >
> > Be reminded that W3C consensus means we have to find a solution that
> > everyone can accept, even though it might not be the one that everyone
> > thinks is the best alternative.
> >
> > To summarise the technical issue as I understand it:
> >
> > * IMSC 1.0.1 includes extensions not in TTML1, defined using syntax in
> > namespaces not defined by TTML1
> > * We want to support the requirements met by those extensions in IMSC 1.1
> > * We want to support the requirements met by those extensions in TTML2
> > * We want IMSC 1.1 to be a subset of TTML2 – there are varying degrees of
> > strength about this amongst the group members, i.e. some want all
> non-TTML2
> > features to be deprecated, others are happy to continue with
> non-deprecated
> > extensions.
> > * It is important to some (maybe all) members that IMSC 1.1 processors be
> > able to process IMSC 1.0.1 documents
> > * We discussed but rejected creating an IMSC 2 that is a pure subset of
> > TTML2 and does not natively support IMSC 1.0.1
> > * It is important to some (but not all) members that TTML2 defines all
> > features in its own namespace
> > * The idea of adopting extensions into TTML2 and making them features
> with
> > no change to their existing namespace was discussed but not adopted.
> There
> > was a formal objection on the grounds that all TTML features must be
> defined
> > in the TTML namespace. There was also a process point that we would need
> to
> > seek permission from EBU for inclusion of EBU namespace extensions.
> >
> > During the TPAC 2017 face to face meeting (minutes) we resolved one of
> two
> > approaches for each feature:
> >
> > 1. In TTML2: include a new feature in a TTML namespace. In IMSC 1.1:
> > deprecate the IMSC 1.0.1 extension AND include the TTML2 feature AND
> provide
> > a mapping from the deprecated extension to the new feature.
> > 2. In TTML2: do not include a new feature. In IMSC 1.1: include the IMSC
> > 1.0.1 extension.
> >
> > Netflix has objected to some of those resolutions within the WG's review
> > period defined under the Decision Policy in the Charter. I have received
> no
> > other objections within that period (which expires at the end of the
> working
> > day today, California time). I have updated and where necessary reopened
> the
> > relevant GitHub issues indicating the objection.
> >
> > * The idea of synonyms or aliases was raised (disclosure: by me),
> discussed
> > but not adopted, i.e. TTML namespace syntax for features where each
> feature
> > is a functional equivalent or superset of an IMSC 1.0.1 extension, and
> both
> > may be supported in IMSC 1.1 with a mapping to the canonical TTML2
> > equivalent. The synonym may additionally be noted informatively in TTML2.
> > The key negative point was that it would encourage the use of both sets
> of
> > syntax in many documents with no clear end point to the practice and no
> > practical benefit. However I cannot recall any formal objection, nor find
> > one in the minutes.
> >
> > The Netflix objection essentially requests that this latter model be
> > adopted, whilst deprecating the IMSC 1.0.1 extensions.
> >
> > Given that I cannot recall any formal objection to the synonym/alias
> > proposal requested by Netflix, I'd like to check if we actually have
> > consensus to adopt it already, i.e. if despite it not being everyone's
> > favourite option, it is something that everyone can nevertheless live
> with.
> >
> > Does anyone object to any of the Netflix proposals? If so, please be
> > specific about the nature of the objection. This will help us to
> construct
> > new proposals.
> >
> > This topic will be on the agenda for next week's call (November 30th),
> but
> > if possible I would like to have a sense of the conclusion or any as yet
> > unraised concerns before the meeting. If anyone would like a call with
> me or
> > others to discuss this informally ahead of the meeting, I am happy to
> > support that, and can be available on Monday 1600-1700 UK time, Tuesday
> > 1630-1730 UK time or Wednesday 1500-1730 UK time.
> >
> > Nigel
> >
> >
> > From: Cyril Concolato <cconcolato@netflix.com>
> > Date: Wednesday, 15 November 2017 at 18:55
> > To: TTWG <public-tt@w3.org>
> > Subject: Objections to TPAC resolutions on IMSC1.1
> > Resent-From: <public-tt@w3.org>
> > Resent-Date: Wednesday, 15 November 2017 at 18:56
> >
> > Dear TTWG experts,
> >
> >
> > Following TPAC, Netflix would like to inform the group that it is not
> > satisfied with some of the resolutions regarding IMSC1.1 and objects to
> > them. Netflix thinks that two important goals must be satisfied in
> defining
> > TTML2 and IMSC1.1:
> >
> > - IMSC1.1 must be a strict-subset of TTML2, aside from deprecated
> features.
> > We believe it is bad practice for W3C to define two TTML-based
> standards, at
> > the same time, which are not compatible with each other.
> >
> > - TTML2 must limit its normative references to Web Platform standards. We
> > believe it is bad practice to have to compile multiple sources of
> > information outside of the Web Platform to implement the standard.
> >
> >
> > Netflix asks for the following actions:
> >
> > a) Marking ittp:activeArea deprecated in IMSC1.1, using a reference to
> > IMSC1.0.1 and no definition in IMSC1.1, in favor of ttp:activeArea,
> > restricted to using two-component values such that ttp:activeArea can be
> > used to do no more than IMSC1.0.1 ittp:activeArea.
> >
> > b) Marking ittp:aspectRatio deprecated in IMSC1.1, using a reference to
> > IMSC1.0.1 and no definition in IMSC1.1, in favor of
> ttp:displayAspectRatio.
> > There does not seem to be a need for restricting ttp:displayAspectRatio.
> >
> > c) Marking itts:forcedDisplay deprecated in IMSC1.1, using a reference to
> > IMSC1.0.1 and no definition in IMSC1.1, in favor of a combination of
> > 'condition' and 'tts:visibility', with the appropriate restrictions on
> > condition such that it remains simple to implement, while at the same
> time
> > offering more flexibility than forcedDisplay.
> >
> > d) Adding the definitions of itts:fillLineGap, ebutts:linePadding and
> > ebutts:multiRowAlign to TTML2, with no change to the semantics, but in
> the
> > TTML namespace; and marking the itts/ebutts version as deprecated in
> > IMSC1.1.
> >
> > e) IMSC1.1 should indicate that when TTML2 features are used in the same
> > document at the same time as their non-TTML2 equivalent and deprecated
> > features, the TTML2 features prevail. This insures that future versions
> of
> > IMSC can effectively remove the features marked as deprecated.
> >
> >
> > Netflix believes that this approach provides clearly designed, forward
> > looking standards, reducing the complexity of the TTML ecosystem.
> >
> >
> > Netflix is aware that this requires an effort of the TTML community as
> > follows:
> >
> > - IMSC1.0.1 renderers do not need to be updated, unless they need to
> support
> > Japanese features. The changes required by the proposed dual syntax and
> > deprecation model are minor compared to them, as they can be implemented
> > using aliases or simple transforms.
> >
> > - Authoring tools already supporting IMSC1.0.1 do not need to migrate to
> the
> > TTML2 syntax, as renderers are required to support both. They only need
> to
> > be updated to support Japanese features. They would need to be updated
> when
> > the deprecated features are removed in a future version.
> >
> > - Specs need to be updated. Netflix is willing to update the TTML2 and
> > IMSC1.1 specs as proposed above.
> >
> > - Test suites need to be updated. For each of the features above, 2
> > additional tests need to be provided: one with the TTML2 flavor and
> without
> > the IMSC1.0.1 flavor; and one with both (testing the override model).
> > Netflix is willing to contribute these tests.
> >
> >
> > We suggest adding these points to the next meeting's agenda.
> >
> >
> > Best regards,
> >
> > Cyril
> >
> >
>
>