Re: {minutes} TTWG Meeting 2015-12-17

On Fri, Dec 18, 2015 at 6:22 AM, Andreas Tai <tai@irt.de> wrote:

> Dear Glenn, all,
>
> Am 17.12.2015 um 20:01 schrieb Glenn Adams:
>
>    atai2: For example, EBU-TT-D, which is a subset of IMSC, also
>>    prohibits the ttp:element and the ttp:attribute. If they were
>>    required in the
>>    ... document then it would be impossible to make EBU-TT-D a
>>    subset of IMSC, so EBU is fine with this.
>>
>> Our review of the EBU-TT-D specification indicates there is no such
> prohibition specified.
>
>
> I think with "review" you refer to an off list exchange about this topic.
> I can only confirm what I said in the meeting yesterday and also in that
> exchange: the EBU-TT-D spec was specified in a way to not allow any other
> TTML vocabulary in a EBU-TT-D instance than explicitly  specified. The
> ttp:profile element and the tt:profile element are not specified and
> therefore are also not allowed. The XML Schema for EBU-TT Part 1 or
> EBU-TT-D would give you a validation error if you would specify these or
> other vocabulary in an EBU-TT-D document.
>
> In your reading there is no restriction on the EBU-TT-D document model on
> the authoring side and in consequence there would be no difference between
> TTML 1 and EBU-TT-D document. This is NOT the case. EBU-TT-D is vocabulary
> subset of TTML 1.
>

I am not saying that EBU-TT-D is not intended to be a subset of TTML1. I am
saying there is nothing I can find in the EBU-TT-D specification in the way
of normative language that leads to a conclusion that the use foreign
vocabulary or TTML vocabulary not otherwise explicitly mentioned is
prohibited from appearing in an EBU-TT-D document instance.

As has been pointed out, the EBU-TT-D schema is informative, so cannot be
used as a definitive indicator of what is permitted (absent specification
text of an explicit prohibition).

If it was indeed the intent of EBU members that the specification prohibit
other vocabulary, such as the use of ttp:profile on the tt:tt element, then
I believe a substantive revision would be required to effect this intent.

At present, given the absence of such language, the statement "the
@ttp:profile attribute is prohibited on the tt:tt element" does not appear
to follow.


>
> If you read it the other way than there is a misunderstanding and from EBU
> groups side we may have to see how we can avoid this kind of misreading of
> the spec in future publications.
>
> Best regards,
>
> Andreas
>
> --
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> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
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