Remove constraint on presence of xml:id (#989).

[skynavga]

Closes #989.

[skynavga]

@nigelmegitt see https://github.com/w3c/ttml2/pull/1162/commits/e716bcb60f070c70dbf0858b26c93d71c4ed7984. It is not necessary to add any informative text re-stating the XML specification that an IDREF must reference a specified ID, and that, as a consequence, the elements referenced by @region and @animate must indeed specify xml:id. Note that the same can be said of @style.

[skynavga]

Need to remove remnants that refer to removed requirement for xml:id in definitions of out-of-line region (animation) terms.

[palemieux]

@skynavga To summarize, the requirement for @xml:id to be present on out-of-line region is simply removed, right?

[skynavga]

Correct

On Wed, Sep 25, 2019 at 12:54 PM Pierre-Anthony Lemieux < notifications@github.com> wrote:

@skynavga https://github.com/skynavga To summarize, the requirement for @xml:id to be present on out-of-line region is simply removed, right?

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[cconcolato]

This would result the same (strange) behavior in TTML1 and TTML2 that if layout contains any region (with or without xml:id they are considered as out-of-line regions), then content does not use a region attribute will not be rendered because no default region would be created. Am I correct?

[skynavga]

@cconcolato correct; I agree it is strange, but that is the current TTML1 behavior, and it is best that TTML2 be consistent with TTML1

[skynavga]

@cconcolato giving this some more thought, we could add a new rule to the [associate region] procedure just after the current rule 3 and before the current rule 4 that states:

if a single, unidentified, i.e., lacking an xml:id attribute, out-of-line region is present, then the element is associated with that region;

this (or its equivalent) could also be back-ported to TTML1 4e.

[nigelmegitt]

@skynavga then what to do if there is more than one unidentified region element child of layout?

I'm not sure that specifying an anonymous default region like that is something that anyone has asked for - it does not seem like a bad idea per se, I'm just aware that we should be resistant to adding features without any documented requirement or use case.

[skynavga]

@nigelmegitt we can conclude this thread at the upcoming call; i'm happy to proceed with the current PR as is, which is consistent with TTML1 as far as I know;

[palemieux]

I do not see a clear use case for the scenario at https://github.com/w3c/ttml2/pull/1162#issuecomment-536098929 , so the resulting, perhaps weird, behavior is not fatal. As indicated in https://github.com/w3c/ttml2/pull/1162#issuecomment-536126863 , we should strive to keep alignment with TTML1. I therefore like the idea of proceeding with the PR as-is.

[css-meeting-bot]

The Timed Text Working Group just discussed Remove constraint on presence of xml:id (#989). ttml2#1162, and agreed to the following:

• RESOLUTION: Proceed with this PR as is and add associated tests.

The full IRC log of that discussion

<nigel> Topic: Remove constraint on presence of xml:id (#989). ttml2#1162
<nigel> github: https://github.com/w3c/ttml2/pull/1162
<nigel> Nigel: [summarises issue]
<nigel> Pierre: My understanding is the proposal is to revert to the constraints of TTML1
<nigel> .. which as was pointed out by many leads to some unexpected outcomes in some corner cases.
<glenn> We have an approval on this already, so given there was no inclination to accept my suggestion to go further, we can go with what we have now.
<nigel> Nigel: This PR removes any sense of definition that an out of line [thing] must have an xml:id and a [thing] without
<nigel> .. an xml:id is not an "out of line" [thing].
<nigel> .. That brings it into line with TTML1.
<nigel> Pierre: Right, I think this is good to go.
<nigel> Nigel: Any other views or questions?
<nigel> group: [no other views]
<nigel> Cyril: So we're favouring consistency with TTML1 even though we know there is a weird behaviour.
<nigel> .. Glenn suggested an option to edit TTML1. Is that an option.
<nigel> Pierre: Unless there's a concrete use case I think we should not bother.
<nigel> .. There's more risk and effort backporting something to TTML1 than leaving it as is.
<nigel> s/option./option?
<nigel> Nigel: I agree I haven't seen a concrete use case.
<nigel> Pierre: There's a bunch of unexpected behaviours but every time we've run into one we've decided that
<nigel> .. if there's no use case we should accept it, and we should continue doing that.
<nigel> Cyril: I don't know if it is a concrete use case but clearly [missed]
<nigel> .. we should at least have tests and check that it is consistent.
<nigel> Pierre: I really like that idea, it's like what we did with some timing corner cases.
<nigel> Nigel: Glenn already mentioned on the issue that he could create validation and presentation tests.
<nigel> Nigel: I think we have consensus to go ahead with this if there are no other points?
<glenn> I need to add tests for this PR before merging anyway, so I can add something for bar and alone unidentified region
<nigel> Cyril: Yes
<nigel> .. A lone unidentified region means nothing will ever be displayed.
<nigel> Pierre: That's right, we should create a test like this, it's an excellent idea.
<glenn> s/bar and alone/bare and alone/
<nigel> PROPOSAL: Proceed with this PR as is and add associated tests.
<nigel> Nigel: Any objections?
<nigel> RESOLUTION: Proceed with this PR as is and add associated tests.

[skynavga]

Tests at w3c/ttml2-tests#234.