Re: Turning TTML2 into Hobo Stew

Note that this is what was agreed and recorded in this issue:
https://github.com/w3c/imsc/issues/265
A PR was merged in applying that: "extensions to [[TTML2]] that are
specified in [[ttml-imsc1.0.1]] are mapped to [[TTML2]] features, and
deprecated."


On Sun, Nov 5, 2017 at 11:35 PM, Glenn Adams <glenn@skynav.com> wrote:

> Let me suggest an alternative approach to muddying the TTML2 spec by
> pulling in foreign namespaces: define a profile of TTML2 and pull those
> foreign namespaces into that profile. Oh, that almost sounds like
> IMSCvNext, doesn't it... You can build on TTML2 in such a profile and bring
> in alternative mechanisms to those defined by TTML2. You can allow authors
> to use either (or both) the TTML2 defined features or (and) non-TTML2
> defined extensions. You can deprecate one or the other as you wish. The
> point being that this approach is already the approach followed by IMSCv1,
> EBU-TT, SMPTE-TT, and others, so just continue that approach in IMSCvNext,
> but don't ask that TTML2 adopt the same approach.
>
> On Sun, Nov 5, 2017 at 10:45 PM, Glenn Adams <glenn@skynav.com> wrote:
>
>> As I predicted, the initial request to incorporate itts:fillLineGap into
>> TTML2 (#429 <https://github.com/w3c/ttml2/issues/429>) has now
>> transformed into a request to incorporate the vocabulary of every profile
>> that extends TTML1 or IMSC1 into TTML2 based solely on the argument that
>> "the industry does it".
>>
>> I find these proposals extremely troubling, and in direct opposition to
>> longstanding design decisions about the nature of TTML2.
>>
>> Let me make clear one of those design decisions: that TTML2 will be
>> syntactically backward compatible with TTML1 AND will define new extensions
>> to TTML1 in existing TTML namespaces (and not non-TTML namespaces).
>>
>> TTML namespaces do not include IMSC namespaces, do not include EBU-TT
>> namespaces, do not include SMPTE namespaces, and do not include any other
>> random namespace that someone happens to claim is used by "the industry".
>>
>> If I was willing to consider adding a single attribute in the itts
>> namespace previously, I am categorically opposed to adding attributes from
>> other namespaces as well, which means, at this point, that I am
>> categorically opposed to adding any IMSC namespace. So I withdraw my prior
>> possible consideration of adding itts:fillLineGap, and now stand opposed to
>> that original proposal.
>>
>> If industry defined profiles that extend TTML1 want to use TTML2, then
>> they need to map their extension vocabulary to TTML2 defined vocabulary,
>> changing the namespaces and names of that vocabulary as required.
>>
>>
>